A102261 a(n) = A002144(n) - A002145(n).

2, 6, 6, 10, 14, 10, 10, 14, 14, 22, 26, 22, 26, 10, 30, 22, 26, 34, 30, 30, 30, 50, 42, 42, 46, 46, 50, 42, 42, 50, 46, 54, 42, 42, 42, 42, 38, 34, 30, 38, 14, 18, 18, 18, 46, 54, 62, 70, 78, 78, 90, 78, 66, 54, 70, 66, 62, 66, 58, 70, 66, 86, 98, 78, 78, 54, 70, 70, 78, 78

Offset

1,1

Comments

a(n) = A108546(2*n+1) - A108546(2*n).

Links

Ivan Neretin, Table of n, a(n) for n = 1..30000

Maple

A002144 := proc(n) option remember ; if n = 1 then RETURN(5) ; fi; for a from procname(n-1)+2 do if isprime(a) and (a mod 4 = 1 ) then RETURN(a) ; fi; od: end; A002145 := proc(n) option remember ; if n = 1 then RETURN(3) ; fi; for a from procname(n-1)+2 do if isprime(a) and (a mod 4 = 3 ) then RETURN(a) ; fi; od: end; A102261 := proc(n) A002144(n)-A002145(n) ; end: seq(A102261(n), n=1..120) ; # R. J. Mathar, Feb 07 2009

Mathematica

nmax = 70; a1 = Select[Range[1, Prime[3*nmax], 4], PrimeQ]; a3 = Select[Range[3, Prime[3*nmax], 4], PrimeQ]; a[n_] := a1[[n]] - a3[[n]]; Table[a[n], {n, 1, nmax}] (* Jean-François Alcover, Dec 17 2013 *)

Crossrefs

Sequence in context: A196053 A063210 A114718 * A245486 A147298 A078636

Adjacent sequences: A102258 A102259 A102260 * A102262 A102263 A102264

Keyword

sign,look

Author

Paul Curtz, Sep 06 2008

Extensions

Edited by N. J. A. Sloane, Sep 06 2008

More terms from R. J. Mathar, Feb 07 2009

Status

approved