OFFSET
1,2
COMMENTS
The primes p of this sequence are those that give the even semiprimes of A268303.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
Marc Chamberland and Karl Dilcher, A Binomial Sum Related to Wolstenholme's Theorem, J. Number Theory, Vol. 171, Issue 11 (Nov. 2009), pp. 2659-2672. See Table 2 p. 2669.
MATHEMATICA
Select[Range[1, 5000, 2], Mod[Binomial[6 #, 2 #], 8] == 7 &] (* Michael De Vlieger, Feb 07 2016 *)
PROG
(PARI) isok(n) = (n%2) && Mod(binomial(6*n, 2*n), 8) == Mod(-1, 8);
(Python)
from __future__ import division
A268304_list, b, m1, m2 = [], 15, [21941965946880, -54854914867200, 49244258396160, -19011472727040, 2933960577120, -126898662960, 771887070, 385943535, 385945560], [10569646080, -25763512320, 22419210240, -8309145600, 1209116160, -46992960, 415800, 311850, 311850]
for n in range(10**3):
if b % 8 == 7:
A268304_list.append(2*n+1)
b = b*m1[-1]//m2[-1]
for i in range(8):
m1[i+1] += m1[i]
m2[i+1] += m2[i] # Chai Wah Wu, Feb 05 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Jan 31 2016
STATUS
approved