OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
ishyp:= proc(n) ormap(t -> t mod 4 = 1, numtheory:-factorset(n)) end proc:
select(ishyp, [seq(i*(i+1)/2, i=1..100)]); # Robert Israel, Jun 02 2023
MATHEMATICA
A212794list[upto_]:=Select[PolygonalNumber[Range[4, upto]], AnyTrue[Map[Mod[First[#], 4]==1&, FactorInteger[#]], TrueQ]&]; A212794list[100] (* Paolo Xausa, Jul 28 2023 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, May 27 2012
STATUS
approved