A251964 -id:A251964 - cp's OEIS frontend

A250131 a(n) is the odd part of the digital sum of 3^n divided by the maximal possible power of 3.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 5, 1, 5, 1, 5, 1, 1, 7, 7, 1, 1, 1, 7, 1, 7, 1, 11, 1, 1, 5, 5, 1, 5, 11, 5, 1, 5, 11, 1, 7, 13, 1, 1, 13, 13, 5, 1, 5, 5, 1, 7, 13, 11, 5, 17, 17, 1, 5, 13, 1, 17, 17, 1, 5, 1, 17, 19, 5, 17, 1

Offset: 1

Graph
List
Refs
Listen
History
Text
Internal format

Vladimir Shevelev, Dec 12 2014

nonn
base

Consider the sequence {b(n)}, such that b(1)=2, b(2)=3, and for n>=3, b(n)=a(n-2). We conjecture that, if we apply the Eratosthenes-like sieve to b(n) and remove 1's, then we obtain a sequence of primes. Peter J. C. Moses noted that these primes follow with some perturbation of order. For example, 73 appears before 71. Similarly, 101 and 103 appear before 97.

Cf. A221858, A225039, A225093, A251964.

a(n) = my(sd = sumdigits(3^n)); sd/(3^(valuation(sd, 3))*2^(valuation(sd, 2))); \\ Michel Marcus, Dec 12 2014

More terms from Peter J. C. Moses, Dec 12 2014

cp's OEIS Frontend

A250131 a(n) is the odd part of the digital sum of 3^n divided by the maximal possible power of 3.

Views

Author

Keywords

Comments

Crossrefs

Programs

PARI

Extensions