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 A227415 a(n) = (n+1)!! mod n!!. 1
 0, 0, 1, 2, 7, 3, 9, 69, 177, 60, 2715, 4500, 42975, 104580, 91665, 186795, 3493665, 13497435, 97345395, 442245825, 2601636975, 13003053525, 70985324025, 64585694250, 57891366225, 3576632909850, 9411029102475, 147580842959550, 476966861546175, 5708173568847750 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS a(n) is divisible by A095987(n+1), and is nonzero for n > 1. - Robert Israel, Mar 10 2016 LINKS Robert Israel, Table of n, a(n) for n = 0..800 FORMULA a(n) = A006882(n+1) mod A006882(n). EXAMPLE a(4) = 5*3 mod 4*2 = 15 mod 8 = 7. MAPLE seq(doublefactorial(n+1) mod doublefactorial(n), n=0..100); # Robert Israel, Mar 10 2016 PROG (Python) for n in range(2, 77):     prOdd = prEven = 1     for i in range(1, n, 2): prOdd *= i     for i in range(2, n, 2): prEven *= i     if n&1: print str(prEven % prOdd)+', ',     else:   print str(prOdd % prEven)+', ', CROSSREFS Cf. A006882, A095987. Cf. A007911: (n-1)!! - (n-2)!! Cf. A007912: (n-1)!! - (n-2)!! (mod n). Cf. A060696: (n-1)!! + (n-2)!! except first two terms. Sequence in context: A256614 A021369 A242304 * A309156 A298042 A051430 Adjacent sequences:  A227412 A227413 A227414 * A227416 A227417 A227418 KEYWORD nonn,easy AUTHOR Alex Ratushnyak, Jul 10 2013 STATUS approved

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Last modified October 20 10:41 EDT 2019. Contains 328257 sequences. (Running on oeis4.)