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 A047905 a(n+1) = a(n) + n (if n is even), a(n+1) = a(n) * n (if n is odd). 8
 1, 1, 3, 9, 13, 65, 71, 497, 505, 4545, 4555, 50105, 50117, 651521, 651535, 9773025, 9773041, 166141697, 166141715, 3156692585, 3156692605, 66290544705, 66290544727, 1524682528721, 1524682528745, 38117063218625, 38117063218651 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..100 MAPLE A047905:=proc(q) local a, n; a:=1; print(a); for n from 2 to q do   a:=1/2*((n-1+a)*(1-(-1)^n)+a*(n-1)*(1+(-1)^n)); print(a); od; end: A047905(1000); # Paolo P. Lava, Feb 19 2013 MATHEMATICA a[0]=1; a[n_]:=a[n]=If[EvenQ[n], a[n-1]+n, a[n-1]n]; Join[{1}, Array[a, 40]] (* Harvey P. Dale, Apr 24 2011 *) nxt[{n_, a_}]:={n+1, If[EvenQ[n], a+n, a*n]}; NestList[nxt, {1, 1}, 30][[All, 2]] (* Harvey P. Dale, Jul 27 2021 *) PROG (Haskell) a047905 n = a047905_list !! (n-1) a047905_list = 1 : zipWith uncurry                            (cycle [(*), (+)]) (zip a047905_list [1..]) -- Reinhard Zumkeller, Nov 13 2013, May 31 2011 (Python) a=1 for n in range(1, 33):     print(a, end=", ")     if n&1:         a *= n     else:         a += n # Alex Ratushnyak, Feb 24 2013 CROSSREFS Cf. A000124, A047904, A077138. Sequence in context: A089147 A094043 A134190 * A134904 A310324 A092476 Adjacent sequences:  A047902 A047903 A047904 * A047906 A047907 A047908 KEYWORD nonn,easy,nice,changed AUTHOR Miklos SZABO (mike(AT)ludens.elte.hu) STATUS approved

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Last modified July 29 03:57 EDT 2021. Contains 346340 sequences. (Running on oeis4.)