OFFSET
1,1
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
A081308(a(n)) = 1.
MATHEMATICA
sp3sQ[n_]:=Length[Select[IntegerPartitions[n, {2}], (PrimeQ[#[[1]]]&&Max[ FactorInteger[#[[2]]][[All, 1]]]<4)||(PrimeQ[#[[2]]]&&Max[ FactorInteger[ #[[1]]][[All, 1]]]<4)&]]==1; Select[Range[500], sp3sQ]/.(5->Nothing) (* Harvey P. Dale, Feb 05 2019 *)
nmax = 1000;
S = Select[Range[nmax], Max[FactorInteger[#][[All, 1]]] <= 3 &];
A081308[n_] := Count[TakeWhile[S, # < n &], s_ /; PrimeQ[n - s]];
Select[Range[nmax], A081308[#] == 1 &] (* Jean-François Alcover, Oct 13 2021 *)
PROG
(Haskell)
a081312 n = a081312_list !! (n-1)
a081312_list = filter ((== 1) . a081308) [1..]
-- Reinhard Zumkeller, Jul 04 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 17 2003
STATUS
approved