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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
OFFSET
1,3
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 * A338119 A297931 A018888
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