OFFSET
1,1
COMMENTS
First differs from A053666 in 26th term.
FORMULA
a(n) = A051801(prime(n)). - Michel Marcus, Mar 11 2022
EXAMPLE
a(25) = 63 because the 25th prime is 97 and 9 * 7 = 63.
a(26) = 1 because the 26th prime is 101, but we ignore the 0 and thus have 1 * 1 = 1.
MAPLE
a:= n-> mul(`if`(i=0, 1, i), i=convert(ithprime(n), base, 10)):
seq(a(n), n=1..77); # Alois P. Heinz, Mar 11 2022
MATHEMATICA
Table[Times@@ReplaceAll[IntegerDigits[Prime[n]], 0 -> 1], {n, 80}] (* Alonso del Arte, Feb 28 2014 *)
PROG
(PARI) a(n) = vecprod(select(x->(x>1), digits(prime(n)))); \\ Michel Marcus, Mar 11 2022
(Python)
from math import prod
from sympy import sieve
def A051801(n): return prod(int(d) for d in str(n) if d != '0')
def a(n): return A051801(sieve[n])
print([a(n) for n in range(1, 78)]) # Michael S. Branicky, Mar 11 2022
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Zak Seidov, Jan 29 2005
STATUS
approved