A125834 Numbers that have exactly 15 representations as a product of two palindromes.

4888884, 8896888, 13345332, 74732526, 100999899, 140732592, 179555376, 269130862, 295777482, 444888444, 734059326, 880968088, 978745768, 1032039008, 1183109928, 1321452132, 1399939992, 1548058512, 1614785172, 1886140256

Offset

1,1

Links

Table of n, a(n) for n=1..20.

Example

4888884 is in the sequence since 4888884 = 1*4888884 = 2*2444442 = 4*1222221 = 11*444444 = 22*222222 = 44*111111 = 111*44044 = 121*40404 = 222*22022 = 242*20202 = 444*11011 = 484*10101 = 1001*4884 = 1221*4004 = 2002*2442.

Mathematica

f[n_]:=f[n]=Length[Select[Divisors[n], #<=n^(1/2)&&FromDigits[ Reverse[IntegerDigits[ # ]]]==#&&FromDigits[Reverse[IntegerDigits [n/# ]]]==n/#&]]; Do[If[f[n]==15, Print[n]], {n, 125000000}]

Crossrefs

Cf. A002113, A116993, A125832, A125833, A125835.

Sequence in context: A361075 A147580 A043662 * A178293 A218108 A089234

Adjacent sequences: A125831 A125832 A125833 * A125835 A125836 A125837

Keyword

base,nonn

Author

Farideh Firoozbakht, Dec 11 2006

Extensions

a(6)-a(20) from Donovan Johnson, Aug 05 2009

Status

approved