A285123 Min(|d(k+1-i) - d(i)|, for i = 1..k), where d(1),..,d(k) are the divisors of prime(n) - 1.

0, 1, 0, 1, 3, 1, 0, 3, 9, 3, 1, 0, 3, 1, 21, 9, 27, 4, 5, 3, 1, 7, 39, 3, 4, 0, 11, 51, 3, 6, 5, 3, 9, 17, 33, 5, 1, 9, 81, 39, 87, 3, 9, 4, 0, 7, 1, 31, 111, 7, 21, 3, 1, 15, 0, 129, 63, 3, 11, 6, 41, 69, 1, 21, 11, 75, 7, 5, 171, 17, 6, 177, 55, 19, 3

Offset

1,5

Links

Clark Kimberling, Table of n, a(n) for n = 1..10000

Formula

a(n)=A056737(A000578(n)).

Example

prime(6) - 1 = 12 has divisors 1,2,3,4,6,12, so that k=6 and d(k+1-i) - d(i) ranges through {-11, -4, -1, 1, 4, 11}, so that a(6) = 1.

Mathematica

f[n_] := f[n] = Prime[n]-1;
Table[Divisors[f[n]] - Reverse[Divisors[f[n]]], {n, 1, 10}]
Table[Min[Abs[Divisors[f[n]] - Reverse[Divisors[f[n]]]]], {n, 1, 100}]

Crossrefs

Cf. A006093, A002378, A056737.

Sequence in context: A110033 A213666 A166407 * A159059 A340262 A346369

Adjacent sequences: A285120 A285121 A285122 * A285124 A285125 A285126

Keyword

nonn,easy

Author

Clark Kimberling, Apr 11 2017

Status

approved