A239619 Base 3 sum of digits of prime(n).

2, 1, 3, 3, 3, 3, 5, 3, 5, 3, 3, 3, 5, 5, 5, 7, 5, 5, 5, 7, 5, 7, 3, 5, 5, 5, 5, 7, 3, 5, 5, 7, 5, 5, 7, 7, 7, 3, 5, 5, 7, 5, 5, 5, 7, 5, 7, 7, 7, 7, 9, 9, 9, 5, 5, 5, 7, 3, 5, 5, 5, 7, 5, 7, 7, 7, 5, 5, 7, 7, 5, 7, 7, 7, 5, 7, 7, 7, 9, 5, 7, 7, 9, 5, 7, 7, 9

Offset: 1

Author

Tom Edgar, Mar 22 2014

Keywords

• nonn
• base
• easy

Examples

			The fifth prime is 11, 11 in base 3 is (1,0,2) so a(5)=1+0+2=3.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007605, A014499, A053735.

Programs

Magma

[&+Intseq(NthPrime(n),3): n in [1..100]]; // Vincenzo Librandi, Mar 25 2014

Mathematica

Table[Plus @@ IntegerDigits[Prime[n], 3], {n, 1, 100}] (* Vincenzo Librandi, Mar 25 2014 *)

PARI

a(n) = vecsum(digits(prime(n), 3)); \\ Michel Marcus, Mar 07 2020

Sage

[sum(i.digits(base=3)) for i in primes_first_n(200)]

Formula

a(n) = A053735(A000040(n)).