OFFSET
1,3
COMMENTS
Indices of double zeros in A255361.
PROG
(Python)
TOP = 10000
a = [0]*TOP
for y in range(2, TOP//2):
for x in range(y, TOP//2):
k = x*y + x + y
if k>=TOP: break
a[k]+=1
print([n for n in range(TOP-1) if a[n]==0 and a[n+1]==0])
(PARI) iszero(n) = {for (y=2, n\2, for (x=y, n\2, if ((x*y+x+y) == n, return(0)); ); ); return (1); }
isok(n) = iszero(n) && iszero(n+1); \\ Michel Marcus, Feb 22 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Feb 21 2015
STATUS
approved