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 A322001 Digits of n interpreted in factorial base: a(Sum d_k*10^k) = Sum d_k*k! 3
 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS More terms than usual are given to distinguish the sequence from A081594, A028897 and A244158, which agree up to a(99). The last two correspond to k! replaced by 2^k resp. Catalan(k). This is a left inverse to A007623 (factorial base representation of n): A322001(A007623(n)) = n for all n >= 0. One could imagine variants which have a(n) = 0 or a(n) = -1 if n is not a term of A007623. Restricted to the range of A007623, it is also a right inverse to A007623, at least up to the 10 digit terms, beyond which A007623 becomes non-injective. LINKS MATHEMATICA a[n_] := Module[{d=Reverse@IntegerDigits[n]}, Sum[d[[i]]*i!, {i, 1, Length[d]}]]; Array[a, 100, 0] (* Amiram Eldar, Nov 28 2018 *) PROG (PARI) A322001(n)=sum(i=1, #n=Vecrev(digits(n)), n[i]*i!) \\ M. F. Hasler, Nov 27 2018 CROSSREFS Cf. A007623 (right inverse), A081594, A028897, A244158. Sequence in context: A156230 A028897 A244158 * A081594 A038506 A091047 Adjacent sequences:  A321998 A321999 A322000 * A322002 A322003 A322004 KEYWORD nonn,base AUTHOR M. F. Hasler, Nov 27 2018 STATUS approved

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Last modified April 5 13:14 EDT 2020. Contains 333241 sequences. (Running on oeis4.)