A274425 Consider van Eck's sequences with a(1)=n and a(2)=0. Sequence lists the index of second occurrence of n.

4, 6, 21, 18, 13, 11, 67, 48, 25, 149, 45, 174, 122, 31, 36, 139, 42, 64, 90, 57, 106, 325, 102, 216, 111, 258, 143, 321, 226, 472, 73, 60, 82, 184, 540, 135, 93, 264, 169, 130, 549, 53, 200, 180, 229, 99, 298, 622, 671, 358, 157, 117, 1487, 476, 1478, 85, 513

Offset

1,1

Links

Paolo P. Lava, Table of n, a(n) for n = 1..1000

Formula

a(n) = 1 + A171862(n). - Jan Ritsema van Eck, Jul 24 2019

Example

Starting with a(1)=1 and a(2)=0 the second occurrence of 1 is for a(4):
1, 0, 0, 1, 3, 0, 3, 2, 0, 3, 3, 1, 8, 0, 5, 0, 2, 9, 0, 3, 9, 3, 2, ...
Starting with a(1)=2 and a(2)=0 the second occurrence of 2 is for a(6):
2, 0, 0, 1, 0, 2, 5, 0, 3, 0, 2, 5, 5, 1, 10, 0, 6, 0, 2, 8, 0, 3, 13, ...
Starting with a(1)=3 and a(2)=0 the second occurrence of 3 is for a(21):
3, 0, 0, 1, 0, 2, 0, 2, 2, 1, 6, 0, 5, 0, 2, 6, 5, 4, 0, 5, 3, 20, 0, ...

Maple

P:=proc(q) local a, c, h, i, k, m, n, p, x; m:=60000; a:=Array(1..m); p:=Array(0..m, -1); c:=Array(0..1000);
for k from 0 to 1000 do for i from 0 to m do p[i]:=0; od; for i from 1 to m do a[i]:=0; od;
a[1]:=k; a[2]:=0; p[0]:=2; p[a[1]]:=1; x:=0; for n from 3 to m do h:=p[x]; a[n]:=x; p[x]:=n; x:=0;
if h>0 then x:=n-h; fi; if a[n]=k then c[k]:=x+1; break; fi;
od; od; [seq(c[n], n=0..1000)]; end: P(1);

Crossrefs

Cf. A171862, A181391, A171911-A171918.

Sequence in context: A027377 A048789 A038069 * A019147 A026722 A323845

Adjacent sequences: A274422 A274423 A274424 * A274426 A274427 A274428

Keyword

nonn,easy

Author

Paolo P. Lava, Jul 13 2016

Status

approved