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A066758 Triangular numbers not divisible by 10 whose reverse is pentagonal. 0
0, 1, 15, 21, 62481, 67896, 2618616, 10095771, 10550121, 5491258003, 103352174628, 299536839001, 7220385308804403, 7686108558349885, 10917127849295955, 724804915074540097006 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..16.

EXAMPLE

51 is pentagonal and 15 is triangular

MATHEMATICA

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

CROSSREFS

Sequence in context: A307792 A236764 A300958 * A297931 A018888 A115174

Adjacent sequences:  A066755 A066756 A066757 * A066759 A066760 A066761

KEYWORD

base,more,nonn

AUTHOR

Erich Friedman, Jan 17 2002

EXTENSIONS

a(13)-a(16) from Lars Blomberg, May 18 2011

Description clarified and offset corrected  by Lars Blomberg, May 29 2011

STATUS

approved

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Last modified October 14 14:42 EDT 2019. Contains 328019 sequences. (Running on oeis4.)