OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..100
EXAMPLE
210276 is a triangular number with k=6 digits and the numbers 210 and 276 are both triangular numbers.
MAPLE
filter:= proc(n) local k;
k:= ceil((1+ilog10(n))/2);
issqr(1+8*floor(n/10^k)) and issqr(1+8*(n mod 10^k))
end proc:
select(filter, [seq(i*(i+1)/2, i=1..20000)]); # Robert Israel, Aug 18 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy, Mar 08 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 17 2002
STATUS
approved