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 A030494 If n is even, 2(n/2 + 1)! - 1; if n is odd, ((n + 1)/2 + 1)! - 1. 0
 1, 3, 5, 11, 23, 47, 119, 239, 719, 1439, 5039, 10079, 40319, 80639, 362879, 725759, 3628799, 7257599, 39916799, 79833599, 479001599, 958003199, 6227020799, 12454041599, 87178291199, 174356582399, 1307674367999, 2615348735999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS MATHEMATICA Table[If[EvenQ[n], 2(n/2 + 1)! - 1, ((n + 1)/2 + 1)! - 1], {n, 40}] (* Alonso del Arte, Feb 19 2020 *) PROG (PARI) a(n)=if(n%2, (n\2+2)!, (n/2+1)!*2) - 1 \\ Charles R Greathouse IV, Mar 27 2020 CROSSREFS s(n) = s(n + 1), where s = A030298. Sequence in context: A290114 A032803 A335883 * A246491 A084361 A077229 Adjacent sequences:  A030491 A030492 A030493 * A030495 A030496 A030497 KEYWORD nonn,easy AUTHOR EXTENSIONS Better description and more terms from Erich Friedman. STATUS approved

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Last modified September 16 12:25 EDT 2021. Contains 347472 sequences. (Running on oeis4.)