A125834 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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