login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A134938
Pentagonal numbers that are the sum of a nonzero pentagonal number and a nonzero square in at least one way.
2
5, 51, 117, 145, 247, 425, 651, 715, 852, 1001, 1247, 1717, 1820, 2147, 2501, 3015, 3151, 4187
OFFSET
1,1
LINKS
MATHEMATICA
Module[{nn=100, pent}, pent=PolygonalNumber[5, Range[nn]]; Select[Flatten[ Outer[ Plus, pent, Range[Sqrt[Max[pent]]]^2]]//Union, IntegerQ[ (1+Sqrt[ 1+24#])/6]&]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 27 2020 *)
CROSSREFS
Sequence in context: A333261 A117710 A064019 * A068540 A208997 A041043
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Jan 21 2008
STATUS
approved