OFFSET
1,3
LINKS
David A. Corneth, Table of n, a(n) for n = 1..10000 (first 4000 terms from Alois P. Heinz)
FORMULA
a(n) = A000607(prime(n)).
a(n) = A168470(n) + 1. - Alonso del Arte, Feb 15 2014, restating the corresponding formula given by R. J. Mathar for A168470.
a(n) = [x^prime(n)] Product_{k>=1} 1/(1 - x^prime(k)). - Ilya Gutkovskiy, Jun 05 2017
EXAMPLE
a(4) = 3 because the 4th prime is 7 which can be partitioned using primes in 3 ways: 7, 5 + 2, and 3 + 2 + 2.
In connection with the 6th prime 13, for instance, we have the a(6) = 9 prime partitions: 13 = 2 + 2 + 2 + 2 + 2 + 3 = 2 + 2 + 2 + 2 + 5 = 2 + 2 + 2 + 7 = 2 + 2 + 3 + 3 + 3 = 2 + 3 + 3 + 5 = 2 + 11 = 3 + 3 + 7 = 3 + 5 + 5.
MAPLE
b:= proc(n, i) option remember; `if`(n=0 or i=2
and n::even, 1, `if`(i=2 or n=1, 0,
b(n, prevprime(i)))+`if`(i>n, 0, b(n-i, i)))
end:
a:= n-> b(ithprime(n)$2):
seq(a(n), n=1..50); # Alois P. Heinz, Sep 15 2016
MATHEMATICA
Table[Count[IntegerPartitions[n], _?(AllTrue[#, PrimeQ]&)], {n, Prime[ Range[ 40]]}] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 07 2015 *)
n=40; ser=Product[1/(1-x^Prime[i]), {i, 1, n}]; Table[SeriesCoefficient[ser, {x, 0, Prime[i]}], {i, 1, n}] (* Gus Wiseman, Sep 14 2016 *)
PROG
(Haskell)
a056768 = a000607 . a000040 -- Reinhard Zumkeller, Aug 05 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Brian Galebach, Aug 16 2000
EXTENSIONS
More terms from James A. Sellers, Aug 25 2000
STATUS
approved