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
Keywords
Examples
97 is the 25th prime number but not a Chen prime since 99 = 3*3*11, therefore 25 is in the sequence.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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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);
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Mathematica
Select[Range[180],Sum[FactorInteger[Prime[ # ]+2][[i,2]],{i,1,Length[ FactorInteger[Prime[ # ] + 2]]}] > 2 &] -
PARI
isok(k) = (bigomega(prime(k)+2) > 2); \\ Michel Marcus, Oct 19 2021
Extensions
Edited by Stefan Steinerberger, Jul 19 2007