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a(1) = 1, a(n) = smallest multiple of a(n-1) > a(n-1) such that a(n) + 1 is a prime.
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%I #10 Jan 19 2023 03:12:28

%S 1,2,4,12,36,72,432,1296,2592,10368,72576,508032,1524096,12192768,

%T 73156608,146313216,438939648,2633637888,23702740992,142216445952,

%U 1991030243328,37829574623232,416125320855552,1664501283422208,6658005133688832,126502097540087808

%N a(1) = 1, a(n) = smallest multiple of a(n-1) > a(n-1) such that a(n) + 1 is a prime.

%H Amiram Eldar, <a href="/A084716/b084716.txt">Table of n, a(n) for n = 1..577</a>

%t a[1] = 1; a[n_] := a[n] = Catch[For[k = 2, True, k++, an = k*a[n - 1]; If[PrimeQ[an + 1], Throw[an]]]]; Table[a[n], {n, 1, 23}] (* _Jean-François Alcover_, Nov 27 2012 *)

%Y Cf. A084717, A084718, A036012.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Jun 11 2003

%E Edited by _Don Reble_, Jun 19 2003