login
A113478
Number of cuban primes less than 10^n.
9
0, 1, 4, 11, 28, 64, 173, 438, 1200, 3325, 9289, 26494, 76483, 221530, 645685, 1895983, 5593440, 16578830, 49347768, 147402214, 441641536, 1326941536, 3996900895, 12066234206, 36501753353
OFFSET
0,3
LINKS
Eric Weisstein's World of Mathematics, Cuban Prime
EXAMPLE
7, 19, 37, 61, 127 are the first few cuban primes, so a(1)=1 and a(2)=4.
PROG
(PARI) A113478(n)=sum(k=1, sqrt(10^n/3), isprime(3*k*(k+1)+1)) \\ M. F. Hasler, Nov 28 2007
CROSSREFS
Sequence in context: A090539 A262050 A293628 * A056601 A370943 A003230
KEYWORD
nonn,more
AUTHOR
Eric W. Weisstein, Jan 10 2006
EXTENSIONS
a(15)-a(18) from Donovan Johnson, Feb 05 2010
a(19)-a(24) from Hiroaki Yamanouchi, Oct 08 2015
STATUS
approved