A115318 Inverse of A115316.

1, 2, 5, 3, 8, 4, 11, 6, 7, 9, 14, 10, 17, 12, 13, 15, 20, 16, 23, 18, 19, 21, 26, 22, 24, 25, 27, 28, 29, 30, 32, 31, 33, 34, 36, 37, 35, 39, 40, 42, 38, 43, 41, 45, 46, 48, 44, 49, 51, 52, 54, 55, 47, 57, 58, 60, 61, 63, 50, 64, 53, 66, 67, 69, 70, 72, 56, 73, 75, 76, 59, 78

Offset

1,2

Links

Table of n, a(n) for n=1..72.

Index entries for sequences that are permutations of the natural numbers

Formula

a(a(n)) = A115319(n).

a(n) = A115316(A115319(n)) = A115319(A115316(n)).

Mathematica

nmax = 72;
nn = nmax + 10; (* estimated length of A115316 - should be increased in case of message "NotFound" in the output *)
np = Ceiling[nn/3] + 1;
nc = Ceiling[(2/3) nn];
pp = Prime[Range[np]];
cc = Partition[Select[Range[FindRoot[n == nc + PrimePi[n] + 1, {n, nc, 2nc}][[1, 2]] // Floor], CompositeQ], 2];
A115316 = Join[{1}, Riffle[pp, cc] // Flatten][[1 ;; nn]];
a[n_] := FirstPosition[A115316, n][[1]];
Table[a[n], {n, 1, nmax}] (* Jean-François Alcover, Nov 15 2021 *)

Crossrefs

Cf. A115316, A115319.

Sequence in context: A186631 A359478 A182184 * A338060 A169856 A185112

Adjacent sequences: A115315 A115316 A115317 * A115319 A115320 A115321

Keyword

nonn

Author

Reinhard Zumkeller, Jan 20 2006

Status

approved