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A250131 a(n) is the odd part of the digital sum of 3^n divided by the maximal possible power of 3. 0

%I

%S 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,

%T 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,

%U 5,13,1,17,17,1,5,1,17,19,5,17,1

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

%C 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.

%o (PARI) a(n) = my(sd = sumdigits(3^n)); sd/(3^(valuation(sd, 3))*2^(valuation(sd, 2))); \\ _Michel Marcus_, Dec 12 2014

%Y Cf. A221858, A225039, A225093, A251964.

%K nonn

%O 1,14

%A _Vladimir Shevelev_, Dec 12 2014

%E More terms from _Peter J. C. Moses_, Dec 12 2014

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Last modified June 19 10:32 EDT 2019. Contains 324219 sequences. (Running on oeis4.)