cp's OEIS Frontend

A026100 a(n) = number of the column of A026098 that contains n.

%I A026100 #14 Jan 18 2020 11:07:45
%S A026100 1,2,1,3,1,2,1,4,3,2,1,4,1,2,3,5,1,5,1,4,3,2,1,6,5,2,6,4,1,7,1,8,3,2,
%T A026100 5,7,1,2,3,6,1,6,1,4,7,9,1,8,7,8,3,4,1,9,5,10,3,2,1,9,1,11,8,12,5,6,1,
%U A026100 4,2,9,1,10,1,2,10,4,7,6,1,11,11,13,1,10,5,14,3,8,1,12,7,3,2,15,5,13,1,11,9,12
%N A026100 a(n) = number of the column of A026098 that contains n.
%H A026100 Antti Karttunen, <a href="/A026100/b026100.txt">Table of n, a(n) for n = 1..19477</a>
%o A026100 (PARI)
%o A026100 getrow(n, all) = {if (n==1, return ([1])); if (n==2, return ([3, 2])); my(row = vector(n)); row[1] = prime(n); for (k=2, n, my(ok = 0, m = 1, val); until(ok, val = m*prime(n+1-k); if (!setsearch(all, val) && !setsearch(Set(row), val), ok = 1); m++; ); row[k] = val; ); return (row); };
%o A026100 A026100list(up_to_row) = { my(all = [], m = Map(), lista = List([]), u); for(n=1, up_to_row, my(row = getrow(n, all)); for(k=1, n, mapput(m,row[k],k)); all = Set(concat(all, row))); for(n=1,oo,if(mapisdefined(m,n,&u), listput(lista,u), if(isprime(n)&&(n>2),listput(lista,1), return(Vec(lista))))); };
%o A026100 v026100 = A026100list(1200);
%o A026100 A026100(n) = v026100[n]; \\ _Antti Karttunen_, Jan 18 2020, after program in A026098 provided by _Michel Marcus_.
%Y A026100 Cf. A026098.
%K A026100 nonn,look
%O A026100 1,2
%A A026100 _Clark Kimberling_
%E A026100 a(27) onward corrected by _Sean A. Irvine_, Sep 15 2019