OFFSET
1,2
COMMENTS
Prime[n] plus a triangular number is prime. - Harvey P. Dale, Jun 12 2013
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
Prime[n]+m*(1+m)/2 is a prime for some m>0.
EXAMPLE
a(2)=4 because prime[2]+(1+2+3+4)=3+10=13 is a prime
MATHEMATICA
Flatten[(Sqrt[1+8#]-1)/2&/@With[{trnos=Accumulate[Range[30]]}, Table[ Select[ trnos, PrimeQ[Prime[n]+#]&, 1], {n, 100}]]] (* Harvey P. Dale, Jun 12 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Jun 29 2003
STATUS
approved