A340872 - OEIS

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A340872

Primes p such that p, p - 1, p - 2 and p - 3 have 2, 4, 6 and 8 divisors respectively.

1019, 226379, 645419, 893099, 967259, 1744859, 1880939, 1996859, 2238779, 2435339, 2999099, 3316619, 3734219, 4092059, 4269899, 4344779, 4511099, 4681739, 4692539, 5857499, 5993579, 6476699, 6744539, 6848939, 6855419, 8160059, 8608619, 8755499, 9254459

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OFFSET

1,1

COMMENTS

Term 55414379 of this sequence is the smallest prime p such that p, p - 1, p - 2, p - 3 and p - 4 have 2, 4, 6, 8 and 10 divisors respectively.

LINKS

Table of n, a(n) for n=1..29.

EXAMPLE

tau (1016) = 8, tau(1017) = 6, tau(1018) = 4, tau(1019) = 2.

MATHEMATICA

Select[Range[10^6], DivisorSigma[0, # - {0, 1, 2, 3}] == {2, 4, 6, 8} &] (* Amiram Eldar, Jan 25 2021 *)

Select[Prime[Range[620000]], DivisorSigma[0, #-{0, 1, 2, 3}]=={2, 4, 6, 8}&] (* Harvey P. Dale, Nov 19 2021 *)

PROG

(Magma) [m: m in [1..10^7] | IsPrime(m) and #Divisors(m - 1) eq 4 and #Divisors(m - 2) eq 6 and #Divisors(m - 3) eq 8]

CROSSREFS

Cf. A000005 (tau), A340871.

Sequence in context: A210139 A245206 A378797 * A104444 A157510 A015160

Adjacent sequences: A340869 A340870 A340871 * A340873 A340874 A340875

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jan 24 2021

STATUS

approved