A119728
Primes p such that p+1, p+2, p+3 and p+4 have equal number of divisors.
Original entry on oeis.org
241, 13781, 19141, 21493, 50581, 61141, 76261, 77431, 94261, 95383, 95413, 98101, 104743, 104869, 134581, 141653, 142453, 152629, 153991, 158341, 160933, 165541, 169111, 199831, 201511, 203431, 206551, 229351, 233941, 235111, 253013, 273367
Offset: 1
241 is a term since 242, 243, 244 and 245 all have 6 divisors:
{1,2,11,22,121,242},{1,3,9,27,81,243},{1,2,4,61,122,244} and {1,5,7,35,49,245}.
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Select[Prime@Range@50000,DivisorSigma[0,#+1]==DivisorSigma[0,#+2]==DivisorSigma[0,#+3]==DivisorSigma[0,#+4]&]
A119730
Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors.
Original entry on oeis.org
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
Offset: 1
13781 is a term 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}.
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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 *)
A119740
Primes p such that p+1, p+2, p+3, p+4, p+5 and p+6 have equal number of divisors.
Original entry on oeis.org
298693, 346501, 1841141, 2192933, 2861461, 3106981, 3375781, 3435589, 3437813, 3865429, 4597013, 6191461, 7016213, 7074901, 7637941, 7918373, 9196309, 10216901, 12798901, 13747429, 14100661, 14171653, 14770981, 14779189
Offset: 1
298693 is a term since 298694, 298695, 298696, 298697, 298698 and 298699 all have 8 divisors:
{1,2,11,22,13577,27154,149347,298694}, {1,3,5,15,19913,59739,99565,298695},
{1,2,4,8,37337,74674,149348,298696}, {1,7,71,497,601,4207,42671,298697},
{1,2,3,6,49783,99566,149349,298698}, {1,19,79,199,1501,3781,15721,298699}.
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Select[Prime@Range[1000000],DivisorSigma[0,#+1]==DivisorSigma[0,#+2]==DivisorSigma[0,#+3]==DivisorSigma[0,#+4]==DivisorSigma[0,#+5]==DivisorSigma[0,#+6]&]
Showing 1-3 of 3 results.