OFFSET
1,1
COMMENTS
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(1) = (3+5)/2 = 4; a(2) = (5+7)/2+(11+13)/2 = 6 + 12 = 18.
MATHEMATICA
ev=Select[Table[(Prime[i]+Prime[i+1])/2, {i, 2, 2000}], EvenQ]; (* sum of next n even interprimes*) i1 := n(n-1)/2+1; i2 := n(n-1)/2+n; A075675=Table[Sum[ev[[i]], {i, i1, i2}], {n, 30}]
Module[{nn=1000, ip, len}, ip=Select[Mean/@Partition[Prime[Range[nn]], 2, 1], EvenQ]; len=Length[ip]; Total/@TakeList[ip, Range[(Sqrt[1+8*len]-1)/2]]] (* Requires Mathematica version 11 or later *) (* Harvey P. Dale, Jun 30 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 24 2002
STATUS
approved