A066741 Pentagonal numbers not divisible by 10 whose reverse is a square.

0, 1, 925, 1426, 6112, 9801, 140301, 52244922262, 1445531162626, 5205252778462, 63253297234426, 9040940929621480310251

Offset

1,3

Comments

a(13) > 2^63. - Donovan Johnson, May 24 2011

Links

Table of n, a(n) for n=1..12.

Example

925 is pentagonal and 529 is square

Mathematica

dtn[L_] := Fold[10#1+#2&, 0, L] A={0}; For[i=1, i>0, i++, t=i(3i-1)/2; r=dtn[Reverse[IntegerDigits[t]]]; If[IntegerQ[Sqrt[r]]&&Mod[t, 10]>0, AppendTo[A, t]; Print[A]]]

Crossrefs

Cf. A000326.

Sequence in context: A172702 A159701 A115696 * A325141 A244169 A245791

Adjacent sequences: A066738 A066739 A066740 * A066742 A066743 A066744

Keyword

base,more,nonn

Author

Erich Friedman, Jan 16 2002

Extensions

a(12) from Donovan Johnson, Apr 03 2008

Offset corrected by Donovan Johnson, May 24 2011

Description clarified and a(12) corrected by Lars Blomberg, May 29 2011

Status

approved