Robert Wintner - cp's OEIS frontend

User: Robert Wintner

Robert Wintner has authored 2 sequences.

A174742 Smallest of three consecutive primes whose sum is not a prime.

2, 3, 13, 37, 43, 47, 59, 73, 89, 97, 103, 107, 113, 127, 131, 137, 151, 167, 173, 179, 181, 191, 193, 199, 223, 227, 233, 239, 241, 251, 257, 263, 269, 277, 307, 313, 317, 331, 353, 359, 367, 373, 383, 397, 419, 421, 433, 439, 443, 461, 479, 487, 503, 521, 523, 541, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613

Offset: 1

Robert Wintner, Nov 30 2010

nonn

Cf. A073681.

[NthPrime(n): n in [1..150] | not IsPrime(NthPrime(n) + NthPrime(n+1) + NthPrime(n+2))]; // Vincenzo Librandi Mar 16 2020

Prime[Select[Range[1000], ! PrimeQ[Prime[#] + Prime[# + 1] + Prime[# + 2]] &]]
Transpose[Select[Partition[Prime[Range[200]],3,1],!PrimeQ[ Total[#]]&]] [[1]] (* Harvey P. Dale, Jun 04 2013 *)

A000040 \ A073681.

A173340 Numbers n for which the factorial of the number of divisors of n is divisible by n.

Original entry on oeis.org

1, 2, 6, 8, 12, 18, 20, 24, 30, 36, 40, 42, 45, 48, 56, 60, 70, 72, 80, 84, 90, 96, 105, 108, 112, 120, 126, 128, 132, 140, 144, 150, 160, 162, 168, 180, 192, 198, 200, 210, 216, 220, 224, 240, 252, 264, 270, 280, 288, 300, 308, 312, 315, 320, 324, 330, 336, 350, 352, 360, 378, 384, 390, 396, 400, 405, 420, 432, 440

Offset: 1

Robert Wintner, Nov 22 2010

nonn

An odd prime p can't be in this sequence because it only has two divisors and 2! does not divide p.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A000005, A000142, A130674.

[ n: n in [1..1000] | Factorial(#Divisors(n)) mod n eq 0 ];

Select[Range[1000], Mod[DivisorSigma[0,#]!, #] == 0 &]

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User: Robert Wintner

A174742 Smallest of three consecutive primes whose sum is not a prime.

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