OFFSET
1,1
COMMENTS
The sequence of numbers representable as x^y + x*y in two or more ways begins: 24, 76, 272, 1044, 2208, 4120, 16412. Example: 2208 = 46^2 + 46*2 = 3^7 + 3*7.
The subsequence of squares begins: 36, 1764.
EXAMPLE
a(2) = 14 = 2^3 + 2*3.
a(3) = 15 = 3^2 + 3*2.
a(22) = 255 = 15^2 + 15*2.
PROG
(PARI) isok(n) = {for (p=2, floor(log(n)/log(2)), for (k=2, sqrtnint(n, p), if (n == k^p + p*k, return (1)); ); ); return (0); } \\ Michel Marcus, Jan 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jan 14 2015
STATUS
approved