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A353302
Numbers k such that A004394(k)-1 and A004394(k)+1 are twin primes.
3
3, 4, 5, 9, 11, 12, 24, 25, 76, 82, 105, 139, 217, 1370
OFFSET
1,1
COMMENTS
a(15) > 10^5, if it exists.
EXAMPLE
3 is a term since the third superabundant number is A004394(3) = 4 and {4-1, 4+1} = {3, 5} is a twin primes pair.
MATHEMATICA
s = {}; abm = 0; k = 0; Do[ab = DivisorSigma[-1, n]; If[ab > abm, abm = ab; k++; If[PrimeQ[n - 1] && PrimeQ[n + 1], AppendTo[s, k]]], {n, 1, 10^6}]; s
CROSSREFS
Intersection of A353300 and A353301.
Sequence in context: A028954 A035247 A321995 * A355159 A039885 A239197
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Apr 10 2022
STATUS
approved