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 A257686 a(0) = 0, for n >= 1: a(n) = A099563(n) * A048764(n). 3
 0, 1, 2, 2, 4, 4, 6, 6, 6, 6, 6, 6, 12, 12, 12, 12, 12, 12, 18, 18, 18, 18, 18, 18, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 72 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS For n >= 1, a(n) = the smallest term of A051683 >= n. Can also be obtained by replacing with zeros all other digits except the first (the most significant) in the factorial base representation of n (A007623), then converting back to decimal. Useful when computing A257687. LINKS Antti Karttunen, Table of n, a(n) for n = 0..5040 FORMULA a(0) = 0, and for n >= 1: a(n) = A099563(n) * A048764(n). Other identities: For all n >= 0, a(n) = n - A257687(n). a(n) = A000030(A007623(n))*(A055642(A007623(n)))! - Indranil Ghosh, Jun 21 2017 EXAMPLE Factorial base representation (A007623) of 2 is "10", zeroing all except the most significant digit does not change anything, thus a(2) = 2. Factorial base representation (A007623) of 3 is "11", zeroing all except the most significant digit gives "10", thus a(3) = 2. Factorial base representation of 23 is "321", zeroing all except the most significant digit gives "300" which is factorial base representation of 18, thus a(23) = 18. PROG (Scheme) (define (A257686 n) (if (zero? n) n (* (A099563 n) (A048764 n)))) (Python) from sympy import factorial as f def a007623(n, p=2): return n if n

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Last modified January 24 00:58 EST 2019. Contains 319404 sequences. (Running on oeis4.)