Shaktipeethas.org

Map showing the locations of these 18 Shakti temples

Bhramaramba /Srisailam (Andhra pradesh)	Mahakali /Ujjain (Madhya pradesh)
Jogulamba /Alampur (Andhra pradesh)	Ekaveera /Mahur (Maharashtra)
Manikyamba (Andhra pradesh)	Maha lakshmi /Kolhapur (Maharashtra)
Puruhutika /Pithapuram (Andhra pradesh)	Girija /Biraja (Orissa)
Kama rupini /Gauhati (Assam)	Sankari (Sri lanka)
Mangala gauri /Gaya (Bihar)	Kamakshi /Kanchi (Tamil nadu)
Vaishnavi /Jwalamukhi (Himachal pradesh)	Shrinkhala (West bengal)
Saraswati /Sarika /Srinagar (Jammu&Kashmir)	Madhaveswari /Lalitha /Prayaga /Allahabad (Uttar pradesh)
Chamundeswari /Mysore (Karnataka)	Visalakshi /Kasi /Varanasi (Uttar pradesh)

This list of Ashtadasa Shakti peethas is collected from a Shloka written by Adi Shankaracharya.

Lankayam shankaridevi , kamakshi kanchikapure /
Pradyumne shrinkhaladevi , chamunda kraunchapattane //

Alampure jogulamba , shrishaile bhramarambika /
Kolhapure mahalakshmi , mahurye ekavirika //

Ujjayinyam mahakali , pithikayam puruhutika /
Odhyane girijadevi , manikya dakshavatike //

Harikshetre kamarupi , prayage madhaveshvari /
Jvalayam vaishnavidevi , gaya mangalyagaurika //

Varanashyam vishalakshi , kashmire tu sarasvati /
Ashtadasha shaktipithani , yoginamapi durlabham //

Sayankale pathennityam , sarvashatrivinashanam /
Sarvarogaharam divyam , sarvasampatkaram shubham //

In this site there are different lists of shaktipeethas 18 shaktipeetas ,51 shaktipeethas
I have a doubt is there any specific importance for the numbers 18,51? if so what they are resembling?

Some people explain a Philosophical meaning for these numbers.

Panchasat (50) Shakti peethas resemble Panchast (50) matrikas (Sanskrit letters).
But we couldn't find a resemblance with the lists of 51 or 52.

Ashtadasa (18) Shakti peethas resemble few important letters out of 50:
a,i,u,am,ah,ka,ca,Ta,ta,pa,nga,nja,Na,na,ma,ya,sa,ksha.

Another logic for 18 Shakti peethas:
This is based on Sanskrit pronounciation:
(udatta+anudatta+swarita)*(hraswa+deergha+pluta)*(anunasika+niranunasika) [3*3*2] =18

3 1/2 Shakti peethas resemble the parts of devine OM:
A,U,M being the three and mmm... (ardha matra) being half.

But many different lists are present. There is no clear info on all of them which can satisfy every body.