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A339968
Numbers k such that sigma(k) and k+2 are relatively prime, where sigma gives the sum of divisors of k.
3
1, 2, 3, 4, 5, 7, 9, 11, 13, 15, 16, 17, 18, 19, 21, 23, 25, 27, 29, 31, 32, 33, 35, 36, 37, 39, 41, 43, 45, 47, 50, 51, 53, 57, 59, 61, 64, 65, 67, 69, 71, 72, 73, 75, 77, 79, 81, 83, 87, 89, 91, 93, 95, 97, 98, 99, 100, 101, 103, 105, 107, 109, 111, 113, 119, 121, 123, 125, 127, 129, 131, 135, 137, 139, 141, 143
OFFSET
1,2
PROG
(PARI) isA339968(n) = (1==gcd(sigma(n), n+2));
CROSSREFS
Positions of ones in A339967.
Cf. also A014567, A339963.
Sequence in context: A064005 A306587 A353301 * A316268 A026285 A013930
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 25 2020
STATUS
approved