A229967 Numbers n such that A229964(n) = 4.

18, 26, 28, 39, 65, 115, 119, 133, 319, 341, 377, 403, 481, 517, 629, 697, 731, 779, 799, 817, 893, 1007, 1207, 1219, 1357, 1403, 1541, 1769, 1943, 2059, 2077, 2117, 2201, 2263, 2291, 2407, 2449, 2573, 2759, 2923, 3071, 3293, 3589, 3649, 3737, 3811, 3827, 3959

Offset: 1

Author

Eric M. Schmidt, Oct 04 2013

Keywords

• nonn

Comments

Equals {18, 26, 28, 39} UNION {pq | p, q prime, p >= 5 and (2p+3 <= q <= 3p-2 or (p == 2 (mod 3) and q = 4p+3))}.

Links

• Eric M. Schmidt, Table of n, a(n) for n = 1..1000
• Rosemary Sullivan and Neil Watling, Independent Divisibility Pairs on the Set of Integers from 1 to N, INTEGERS, Electronic J. of Combinatorial Number Theory, Vol. 13, Paper A65, 2013.

Crossrefs

Cf. A166684, A082663, A229965, A229966.

Programs

Sage

sum(([p * q for q in prime_range(2*p+3, 3*p-1)] for p in prime_range(5, 10000)), []) + [p * (4*p + 3) for p in prime_range(5, 10000) if (4*p+3).is_prime() and p%3==2] + [18, 26, 28, 39]