A249735 - OEIS

%I #15 Dec 13 2014 00:37:46

%S 1,5,7,11,25,13,17,35,19,23,55,29,49,125,31,37,65,77,41,85,43,47,175,

%T 53,121,95,59,91,115,61,67,275,119,71,145,73,79,245,143,83,625,89,133,

%U 155,97,187,185,161,101,325,103,107,385,109,113,205,127,203,425,209,169,215,343,131,235,137,253,875,139,149,265,221,217,605,151

%N Odd bisection of A003961: Replace in 2n-1 each prime factor p(k) with prime p(k+1).

%C This has the same terms as A007310 (Numbers congruent to 1 or 5 mod 6), but in different order. Apart from 1, they are the numbers that occur below the first two rows of arrays like A246278 and A083221 (A083140).

%H Antti Karttunen, <a href="/A249735/b249735.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A003961(2n - 1).

%F a(n) = A007310(A249746(n)). [Permutation of A007310, Numbers congruent to 1 or 5 mod 6.]

%F Other identities. For all n >= 1:

%F A007310(n) = a(A249745(n)).

%F A246277(5*a(A048673(n))) = n.

%F A246277(5*a(n)) = A064216(n).

%o (Scheme) (define (A249735 n) (A003961 (+ n n -1)))

%Y Cf. A249734 (the other bisection of A003961).

%Y Cf. also A007310 (A038179), A249746.

%K nonn

%O 1,2

%A _Antti Karttunen_, Nov 23 2014