OFFSET
1,1
COMMENTS
Oblong numbers are numbers of the form k*(k+1) (A002378).
LINKS
Robert Israel and Giovanni Resta, Table of n, a(n) for n = 1..391 (terms < 10^25, first 221 terms from Robert Israel)
MAPLE
filter:= proc(x) local t; t:= convert(convert(x, base, 10), `*`);
t > 0 and issqr(1+4*t); end proc:
select(filter, [seq(x*(1+x), x=1..10^4)]); # Robert Israel, Apr 14 2017
MATHEMATICA
f[x_] := Sqrt[1 + 4 (Times @@ IntegerDigits[x])]; Select[Table[n (n + 1), {n, 1, 10000}], f[#] > 1 && Mod[f[#], 2] == 1 &]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Melvin Peralta, Apr 09 2017
STATUS
approved