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A190355 Numbers n such that d(n-1)=d(n+1)=12 where d(k)=A000005(k) (number of divisors of k). 3
199, 307, 341, 349, 351, 415, 491, 737, 739, 851, 949, 1013, 1061, 1149, 1205, 1211, 1275, 1277, 1313, 1315, 1421, 1667, 1695, 1747, 1925, 2049, 2149, 2276, 2357, 2365, 2683, 2717, 2827, 2889, 2891, 2949, 3051, 3115, 3173, 3259, 3475, 3581, 3651, 3797, 4013, 4045, 4149, 4193, 4449, 4597, 4627, 4654, 4843 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

A000005(a(n)-1) = A000005(a(n)+1) = 12.

MATHEMATICA

Select[Range[2, 8000], DivisorSigma[0, # - 1] == 12 && DivisorSigma[0, # + 1] == 12 &] (* G. C. Greubel, Dec 29 2017 *)

SequencePosition[DivisorSigma[0, Range[5000]], {12, _, 12}][[All, 1]]+1 (* Harvey P. Dale, Jul 21 2021 *)

PROG

(PARI) for(n=2, 10^4, if( numdiv(n-1)==12 && numdiv(n+1)==12, print1(n, ", "))); /* Joerg Arndt, May 13 2011 */

CROSSREFS

Cf. A189974, A190267.

Sequence in context: A142232 A166459 A304368 * A213078 A142682 A088294

Adjacent sequences:  A190352 A190353 A190354 * A190356 A190357 A190358

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, May 09 2011

EXTENSIONS

Terms corrected by R. J. Mathar, May 25 2011

STATUS

approved

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Last modified May 25 18:25 EDT 2022. Contains 354071 sequences. (Running on oeis4.)