cp's OEIS Frontend

A064554 a(n) = Min {k | A064553(k) = n}.

%I A064554 #20 Sep 11 2018 05:01:50
%S A064554 1,2,3,4,7,6,13,8,9,14,29,12,37,26,21,16,53,18,61,28,39,58,79,24,49,
%T A064554 74,27,52,107,42,113,32,87,106,91,36,151,122,111,56,173,78,181,116,63,
%U A064554 158,199,48,169,98,159,148,239,54,203,104,183,214,271,84,281,226,117,64
%N A064554 a(n) = Min {k | A064553(k) = n}.
%C A064554 A064553(a(n)) = n and A064553(a(k)) <> k for k < a(n). For prime p, a(p)=prime(p-1), which is sequence A055003. - _T. D. Noe_, Dec 12 2004
%C A064554 a(n) is not multiplicative because a(7*13) = a(91) = 463, but a(7)*a(13) = 13*37 = 481 and 91 is the smallest possible such n. - _Christian G. Bower_, May 19 2005
%C A064554 a(n) = A080688(n,1). - _Reinhard Zumkeller_, Oct 01 2012
%C A064554 Minimal shifted Heinz number of a factorization of n, where the shifted Heinz number of a factorization (y_1, ..., y_k) is prime(y_1 - 1) * ... * prime(y_k - 1). - _Gus Wiseman_, Sep 05 2018
%H A064554 T. D. Noe, <a href="/A064554/b064554.txt">Table of n, a(n) for n = 1..8000</a>
%H A064554 T. D. Noe, <a href="/A064554/a064554.gif">Plot of A064554</a>
%t A064554 facs[n_]:=If[n<=1,{{}},Join@@Table[(Prepend[#1,d]&)/@Select[facs[n/d],Min@@#1>=d&],{d,Rest[Divisors[n]]}]];
%t A064554 Table[Min[Times@@Prime/@(#-1)&/@facs[n]],{n,100}] (* _Gus Wiseman_, Sep 05 2018 *)
%o A064554 (Haskell)
%o A064554 a064554 = head . a080688_row  -- _Reinhard Zumkeller_, Oct 01 2012
%Y A064554 Cf. A064555, A001055, A064553.
%Y A064554 Cf. A055003 (prime(prime(n)-1)).
%Y A064554 Cf. A007716, A056239, A162247, A215366, A246868, A318871.
%K A064554 nonn
%O A064554 1,2
%A A064554 _Reinhard Zumkeller_, Sep 21 2001