OFFSET
1,1
COMMENTS
Zhi-Wei SUN conjectured that n=216 is the only number not of the form n = p + k(k+1)/2 with p a prime or zero and more precisely that the numbers given in this sequence A137996(1..123) = 2,...,88956 are the only numbers which cannot be written in this form with p=0 or p=1 (mod 4).
LINKS
Zhi-Wei SUN, A new conjecture: n=p+x(x+1)/2, Mar 23, 2008.
PROG
(PARI) { for( n=1, 10^8, t=sqrtint(2*n); if( 0 >= p =n-t*(t+1)/2, !p & next, isprime(p) & p%4==1 & next); until( !t--, isprime( p+=t ) & p%4==1 & next(2)); print1(n", "))}
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Mar 24 2008
STATUS
approved