A061120 Compute sum of divisors of the prime(n+1)-prime(n)-1 composite numbers between two consecutive primes; choose the smallest.

7, 12, 13, 28, 24, 39, 32, 31, 72, 48, 56, 96, 72, 57, 72, 168, 84, 96, 195, 96, 121, 108, 112, 156, 216, 162, 280, 152, 133, 176, 160, 288, 168, 372, 192, 192, 252, 183, 240, 546, 216, 508, 294, 468, 240, 252, 342, 560, 384, 288, 744, 280, 288, 304, 324, 720

Offset

2,1

Links

Michael S. Branicky, Table of n, a(n) for n = 2..10001 (terms 2..1002 from Harry J. Smith)

Formula

a(n) = Min{sigma(c); p(n+1) > c > p(n)}, c is composite, p(n) is the n-th prime and sigma=A000203().

Prog

(PARI) { n=1; q=3; m=10^6; forprime (p=5, prime(1003), a=m; for (i=q + 1, p - 1, a=min(sigma(i), a)); q=p; write("b061120.txt", n++, " ", a) ) } \\ Harry J. Smith, Jul 18 2009
(Python)
from sympy import prime, divisor_sigma as sigma
def a(n): return min(sigma(c) for c in range(prime(n)+1, prime(n+1)))
print([a(n) for n in range(2, 58)]) # Michael S. Branicky, Jul 12 2021

Crossrefs

Cf. A000040, A000203, A061141, A335579.

Sequence in context: A048653 A205807 A075696 * A078835 A173417 A031021

Adjacent sequences: A061117 A061118 A061119 * A061121 A061122 A061123

Keyword

nonn

Author

Labos Elemer, May 29 2001

Extensions

Offset changed by Michael S. Branicky, Jul 12 2021

Status

approved