login
A081313
Numbers having more than one representation as sum of a prime and a 3-smooth number.
4
4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 53, 55, 56, 57, 59, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 86
OFFSET
1,1
LINKS
FORMULA
A081308(a(n)) > 1.
MATHEMATICA
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)
a081313 n = a081313_list !! (n-1)
a081313_list = filter ((> 1) . a081308) [1..]
-- Reinhard Zumkeller, Jul 04 2012
CROSSREFS
Subsequence of A081311.
Sequence in context: A359740 A171463 A020705 * A227983 A081333 A026419
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 17 2003
STATUS
approved