A065992 Numbers k such that the sum of the nonsquare numbers from 1 to k is a square.

6, 12, 31, 40, 411, 1638, 2352, 9465, 263284, 647498, 1227466, 3179974, 4027111, 5382959, 29444851, 32585267, 50402546, 52610042, 98185445, 3750320631, 14471636075, 79389982446, 157183654414

Offset

1,1

Comments

a(24) > 2*10^12. - Donovan Johnson, Jan 16 2011

Links

Table of n, a(n) for n=1..23.

Example

12 is in the sequence because 2 + 3 + 5 + 6 + 7 + 8 + 10 + 11 + 12 = 64 = 8*8.

Prog

(PARI) isA065992(n) = {local(m); m=floor(sqrt(n)); if(n<2, 0, issquare((n*(n+1)/2)-(m*(m+1)*(2*m+1)/6)))} \\ Michael B. Porter, Feb 02 2010

Crossrefs

Sequence in context: A119626 A152522 A096356 * A263587 A085611 A122608

Adjacent sequences: A065989 A065990 A065991 * A065993 A065994 A065995

Keyword

nonn

Author

Jonathan Ayres (jonathan.ayres(AT)ntlworld.com), Dec 10 2001

Extensions

a(20)-a(23) from Donovan Johnson, Jan 16 2011

Status

approved