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A119730 Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors. 0
13781, 19141, 21493, 50581, 142453, 152629, 253013, 298693, 307253, 346501, 507781, 543061, 845381, 1079093, 1273781, 1354501, 1386901, 1492069, 1546261, 1661333, 1665061, 1841141, 2192933, 2208517, 2436341, 2453141, 2545013 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..27.

EXAMPLE

13781 is OK since 13782, 13783, 13784, 13785 and 13786 all have 8 divisors:

{1,2,3,6,2297,4594,6891,13782}, {1,7,11,77,179,1253,1969,13783},

{1,2,4,8,1723,3446,6892,13784}, {1,3,5,15,919,2757,4595,13785} and

{1,2,61,113,122,226,6893,13786}.

MATHEMATICA

Select[Prime@Range[1000000], DivisorSigma[0, #+1]==DivisorSigma[0, #+2]==DivisorSigma[0, #+3]==DivisorSigma[0, #+4]==DivisorSigma[0, #+5]&]

endQ[n_]:= Length[Union[DivisorSigma[0, (n + Range[5])]]]==1; Select[Prime[ Range[ 200000]], endQ] (* Harvey P. Dale, Jan 16 2019 *)

CROSSREFS

Cf. A008329, A049234.

Sequence in context: A235184 A270639 A031807 * A204839 A208487 A188102

Adjacent sequences:  A119727 A119728 A119729 * A119731 A119732 A119733

KEYWORD

nonn

AUTHOR

Zak Seidov, Jul 29 2006

STATUS

approved

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Last modified December 6 04:14 EST 2019. Contains 329784 sequences. (Running on oeis4.)