A118499 Numbers k such that the k-th prime number is not a Chen prime.

14, 18, 21, 22, 25, 27, 36, 38, 40, 44, 48, 50, 53, 58, 59, 61, 65, 67, 70, 73, 74, 76, 78, 82, 84, 85, 88, 90, 99, 101, 108, 110, 111, 112, 114, 117, 121, 122, 125, 127, 129, 130, 131, 134, 137, 143, 147, 149, 153, 155, 158, 163, 168, 170

Offset

1,1

Links

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

Example

97 is the 25th prime number but not a Chen prime since 99 = 3*3*11, therefore 25 is in the sequence.

Maple

ts_inde_nonchen:= proc(n) local i, ans, inde; ans:=[ ]: inde := 0; for i from 1 to n do if ( isprime(i) = 'true') then inde:=inde+1: if (isprime(i+2) = 'false' and numtheory[bigomega](i+2) <> 2) then ans:=[ op(ans), inde ] fi fi od: return ans end: ts_inde_nonchen(2000);

Mathematica

Select[Range[180], Sum[FactorInteger[Prime[ # ]+2][[i, 2]], {i, 1, Length[ FactorInteger[Prime[ # ] + 2]]}] > 2 &]

Prog

(PARI) isok(k) = (bigomega(prime(k)+2) > 2); \\ Michel Marcus, Oct 19 2021

Crossrefs

Cf. A102540, A109611.

Sequence in context: A060504 A052026 A317743 * A111205 A097324 A051419

Adjacent sequences: A118496 A118497 A118498 * A118500 A118501 A118502

Keyword

nonn

Author

Jani Melik, May 05 2006

Extensions

Edited by Stefan Steinerberger, Jul 19 2007

Status

approved