A190645 Numbers n such that d(n-2) = d(n) = d(n+2) = 12 where d(n)=A000005(n).

350, 738, 1276, 1314, 2890, 5052, 6356, 9052, 9054, 9950, 14050, 15966, 16852, 17916, 17948, 19166, 19852, 22475, 23348, 23420, 24350, 25182, 25184, 25186, 30476, 32418, 41058, 41060, 47646, 47648, 54927, 56452, 57436, 59924, 61794, 61796, 66787, 68348

Offset

1,1

Comments

Numbers of the form A190355(n)+1 such that A190355(n)=A190355(n+1)-2.

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

Mathematica

f[n_] := DivisorSigma[0, n]; lst = {}; n = 2; While[Length[lst] < 40, n++; If[f[n-2] == f[n] == f[n+2] == 12, AppendTo[lst, n]]]; lst (* T. D. Noe, May 26 2011 *)
Select[Range[2, 5000], DivisorSigma[0, # - 2] == 12 && DivisorSigma[0, #] == 12 && DivisorSigma[0, # + 2] == 12 &] (* G. C. Greubel, Dec 29 2017 *)

Prog

(PARI) isok(n) = (n>2) && (numdiv(n-2)==12) && (numdiv(n)==12) && (numdiv(n+2)==12); \\ Michel Marcus, Dec 30 2017

Crossrefs

Cf. A000005(number of divisors of n), A190355.

Sequence in context: A109762 A074055 A304282 * A349952 A108776 A184609

Adjacent sequences: A190642 A190643 A190644 * A190646 A190647 A190648

Keyword

nonn

Author

Juri-Stepan Gerasimov, May 15 2011

Extensions

Corrected and extended by T. D. Noe, May 26 2011

Status

approved