OFFSET
1,1
EXAMPLE
211 = P(5) + P(11) = P(1) + P(12) = 35 + 176 = 1 + 210, where P(n) is the n-th pentagonal number A000326.
PROG
(PARI) is(k) = sum(i=1, sqrt(1+12*k)\6, sqrt(1+24*k+12*i-36*i*i)%6==5) == 2; \\ Jinyuan Wang, Mar 06 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Olivier Gérard, Mar 05 2020
STATUS
approved