cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A166037 Numbers that are the sum of 2 successive nonprimes A141468.

Original entry on oeis.org

1, 5, 10, 14, 17, 19, 22, 26, 29, 31, 34, 38, 41, 43, 46, 49, 51, 53, 55, 58, 62, 65, 67, 69, 71, 74, 77, 79, 82, 86, 89, 91, 94, 97, 99, 101, 103, 106, 109, 111, 113, 115, 118, 122, 125, 127, 129, 131, 134, 137, 139, 142, 146, 149, 151, 153, 155, 158, 161, 163, 166
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Oct 05 2009

Keywords

Comments

a(n) = (n-1)-th nonprimes + (n-1)-th composites for n >= 2. a(n) = A018252(n-1) + A002808(n-1) for n >= 2. - Jaroslav Krizek, Dec 13 2009

Examples

			a(1) = 0 + 1 =  1;
a(2) = 1 + 4 =  5;
a(3) = 4 + 6 = 11.
		

Crossrefs

Cf. A167915 (primes that are the sums of two consecutive composites).

Programs

  • Maple
    A002808 := proc(n) option remember; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; fi; od: fi; end: A141468 := proc(n) if n <= 2 then n-1 ; else A002808(n-2) ; fi; end: A166037 := proc(n) A141468(n)+A141468(n+1) ; end: seq(A166037(n),n=1..120) ; # R. J. Mathar, Oct 10 2009
  • Mathematica
    With[{nn=100},Join[{1},Total/@Partition[Complement[Range[nn],Prime[ Range[ PrimePi[ nn]]]],2,1]]] (* Harvey P. Dale, Aug 03 2014 *)