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a(0) = 1; for n >= 1, a(n) = A275732(n) * A003961(a(A257684(n))).
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%I #21 Jun 21 2017 03:06:45

%S 1,2,3,6,3,6,5,10,15,30,15,30,5,10,15,30,15,30,5,10,15,30,15,30,7,14,

%T 21,42,21,42,35,70,105,210,105,210,35,70,105,210,105,210,35,70,105,

%U 210,105,210,7,14,21,42,21,42,35,70,105,210,105,210,35,70,105,210,105,210,35,70,105,210,105,210,7,14,21,42,21,42

%N a(0) = 1; for n >= 1, a(n) = A275732(n) * A003961(a(A257684(n))).

%C a(n) = product of primes whose indices are positions of nonzero-digits in factorial base representation of n (see A007623). Here positions are one-based, so that the least significant digit is the position 1, the next least significant the position 2, etc.

%H Antti Karttunen, <a href="/A275733/b275733.txt">Table of n, a(n) for n = 0..40320</a>

%H Indranil Ghosh, <a href="/A275733/a275733.txt">Python program for computing this sequence</a>

%H <a href="/index/Fa#facbase">Index entries for sequences related to factorial base representation</a>

%F a(0) = 1; for n >= 1, a(n) = A275732(n) * A003961(a(A257684(n))).

%F Other identities and observations. For all n >= 0:

%F a(A007489(n)) = A002110(n).

%F A001221(a(n)) = A001222(a(n)) = A060130(n).

%F A048675(a(n)) = A275727(n).

%F A061395(a(n)) = A084558(n).

%e For n=19, A007236(19) = 301, thus a(19) = prime(3)*prime(1) = 5*2 = 10.

%e For n=52, A007236(52) = 2020, thus a(52) = prime(2)*prime(4) = 3*7 = 21.

%o (Scheme, with memoization-macro definec)

%o (definec (A275733 n) (if (zero? n) 1 (* (A275732 n) (A003961 (A275733 (A257684 n))))))

%Y Cf. A001221, A002110, A003961, A005117, A007489, A007623, A048675, A060130, A061395, A084558, A257684, A275732.

%Y Subsequence of A005117.

%Y Cf. A275727.

%Y Cf. also A275725, A275734, A275735 for other such prime factorization encodings of A060117/A060118-related polynomials.

%K nonn

%O 0,2

%A _Antti Karttunen_, Aug 08 2016