OFFSET
0,3
EXAMPLE
a(2)=3 because 2nd triangular number is 3 and all three of 3-0=3, 3-1=2 and 6-3=3 are prime [n=2 is the only case where there is multiplicity].
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Jun 27 2000
STATUS
approved