A378417 a(n) is the least k such that A127064(k) = n.

0, 1, 2, 3, 4, 17, 24, 62, 68, 162, 169, 176, 183, 188, 369, 694, 897, 988, 1027, 4183, 5510, 6063, 6341, 6444, 6465, 25787, 32844, 37722, 38811, 39450, 151679, 200946, 226703, 240056, 248947, 430398, 612633, 633473, 635344, 637227, 637237, 637256, 637306, 1095790, 1353912, 1554970, 7045573

Offset

1,3

Comments

a(n) is the least k such that n - 1 iterations of A004648 (k -> prime(k) (mod k)) are needed to reach 0.

Links

Table of n, a(n) for n=1..47.

Formula

A127064(a(n)) = n.

Example

a(6) = 17 because 5 iterations of A004648 starting at 17 result in 0, and every k < 17 requires fewer iterations:
  prime(17) (mod 17) = 59 (mod 17) = 8
  prime(8) (mod 8) = 19 (mod 8) = 3
  prime(3) (mod 3) = 5 (mod 3) = 2
  prime(2) (mod 2) = 3 (mod 2) = 1
  prime(1) (mod 1) = 2 (mod 1) = 0.

Maple

P:= select(isprime, [2, seq(i, i=3..10^8, 2)]): nP:= nops(P):
V:= Array(0..nP): count:= 0: R[1]:= 0:
for n from 1 to nP do
V[n]:= V[P[n] mod n]+1;
if V[n] > count then count:= count+1; R[count]:= n fi;
od:
seq(R[i], i=1..count);

Crossrefs

Cf. A004648, A127064.

Sequence in context: A111191 A333825 A115891 * A359230 A293035 A037394

Adjacent sequences: A378414 A378415 A378416 * A378418 A378419 A378420

Keyword

nonn

Author

Robert Israel, Nov 25 2024

Status

approved