A226176 Refactorable numbers between a pair of twin primes.

12, 18, 60, 72, 108, 180, 228, 240, 348, 600, 828, 882, 1152, 1620, 1668, 1788, 2088, 2340, 2688, 3120, 3168, 3252, 3360, 3372, 3528, 3852, 4050, 4128, 4548, 4788, 4932, 5280, 5520, 5652, 5868, 6660, 6828, 6948, 6960, 7212, 7308, 8292, 8388, 8628, 9012

Offset

1,1

Comments

Refactorable numbers that are the averages of twin pairs.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[10000], PrimeQ[# - 1] && PrimeQ[# + 1] && Mod[#, DivisorSigma[0, #]] == 0 &] (* T. D. Noe, Jun 03 2013 *)

Prog

(PARI) p=2; forprime(q=3, 1e4, if(q-p==2 && (p+1)%numdiv(p+1)==0, print1(p+1", ")); p=q) \\ Charles R Greathouse IV, Mar 18 2014

Crossrefs

Cf. A014574, A033950.

Sequence in context: A279369 A119147 A370395 * A177426 A232384 A086301

Adjacent sequences: A226173 A226174 A226175 * A226177 A226178 A226179

Keyword

nonn

Author

Irina Gerasimova, May 29 2013

Status

approved