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A049103 Numbers k such that k and k+1 both have 6 divisors. 6
44, 75, 98, 116, 147, 171, 242, 243, 244, 332, 387, 507, 548, 603, 604, 724, 844, 908, 931, 963, 1075, 1083, 1251, 1324, 1412, 1467, 1556, 1587, 1675, 1772, 2523, 2524, 2636, 2644, 2763, 3283, 3356, 3411, 3508, 3788, 3987, 4075, 4203, 4204, 4418, 4491, 4804, 4868, 4923, 4924 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, 1986, entry 44, p. 103.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Vincenzo Librandi)

FORMULA

a(n) = A049104(n) - 1. - Zak Seidov, Feb 11 2016

MATHEMATICA

Flatten[Position[Partition[Table[DivisorSigma[0, n], {n, 5000}], 2, 1], _?(# == {6, 6}&)]] (* Harvey P. Dale, Apr 09 2012 *)

PROG

(PARI) isok(n) = (numdiv(n) == 6) && (numdiv(n+1) == 6); \\ Michel Marcus, Feb 11 2016

CROSSREFS

Intersection of A005237 and A030515.

Cf. A038400, A049104.

Sequence in context: A242515 A156812 A171665 * A074172 A039386 A043209

Adjacent sequences:  A049100 A049101 A049102 * A049104 A049105 A049106

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Felice Russo, Olivier Gérard

STATUS

approved

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Last modified November 29 04:03 EST 2020. Contains 338756 sequences. (Running on oeis4.)