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 A068858 a(1) = 3 = 1*3; a(n) = smallest multiple of a(n-1) which is a product of two consecutive odd numbers. 1
 3, 15, 195, 4095, 2477475, 448422975, 19384876786275, 70676639845770308825475, 11604095937711402889585984522057770447375, 56023729629975618843823135187551800751351023283966800458449243286895375 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 195 = 13*15 belongs to this sequence and the smallest multiple of 195 which is a product of two consecutive odd numbers is 4095 = 63*65. MAPLE f:= proc(x) local V, V1, y;      V:= map(t -> rhs(op(t))-1, [msolve(r^2=1, x)]);      V:= map(t -> `if`(t*(t+2)=x, t + x, t), V);      y:= min(map(t -> `if`(t::even, t+x, t), V));      y*(y+2) end proc: A[1]:= 3: for n from 2 to 11 do A[n]:= f(A[n-1]) od: seq(A[i], i=1..11); # Robert Israel, May 14 2017 CROSSREFS Cf. A068857. Sequence in context: A087614 A063739 A060194 * A280772 A166359 A195515 Adjacent sequences:  A068855 A068856 A068857 * A068859 A068860 A068861 KEYWORD nonn AUTHOR Amarnath Murthy, Mar 12 2002 EXTENSIONS More terms from Sascha Kurz, Mar 23 2002 Corrected by Robert Israel, May 14 2017 STATUS approved

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Last modified October 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)