A135502 - OEIS

A135502

Admirable numbers in the middle of twin primes.

12, 30, 42, 102, 138, 270, 282, 618, 642, 822, 1488, 1698, 1878, 2082, 2238, 2382, 2658, 2802, 3462, 3558, 3918, 4638, 4722, 5442, 6198, 6702, 8538, 8598, 9678, 10938, 12162, 12378, 12822, 12918, 13218, 13722, 13758, 13998, 14082, 16062, 17418

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OFFSET

1,1

COMMENTS

Numbers n such that n is admirable, n-1 is prime and n+1 is prime.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

A014574 INTERSECT A111592. - R. J. Mathar, Feb 10 2008

EXAMPLE

30 is in the sequence, as 29=30-1 and 31=30+1 are a pair of twin primes.

MATHEMATICA

Select[Range[18000], MemberQ[Most[Divisors[#]], (DivisorSigma[1, #]-2#)/2]&&AllTrue[#+{1, -1}, PrimeQ]&] (* Harvey P. Dale, Sep 11 2023 *)

CROSSREFS

Cf. A111592, A001359, A006512.

Sequence in context: A108278 A364975 A298077 * A256620 A125582 A031107

Adjacent sequences: A135499 A135500 A135501 * A135503 A135504 A135505

KEYWORD

easy,nonn

AUTHOR

Olaf Voß, Feb 09 2008

STATUS

approved