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A074625 Triangular array T(n,k) (n >= 1, 1 <= k <= n) read by rows, where T(n,k) = smallest number x such that Mod[sigma[x],n]=k. 6
1, 1, 3, 1, 7, 2, 1, 5, 2, 3, 1, 4, 2, 3, 8, 1, 7, 2, 3, 2401, 5, 1, 29, 2, 3, 6, 5, 4, 1, 10, 2, 3, 9, 5, 4, 7, 1, 19, 2, 3, 13, 5, 4, 7, 10, 1, 6, 2, 3, 8, 5, 4, 7, 18, 19, 1, 9, 2, 3, 24, 5, 4, 7, 16, 21, 43, 1, 13, 2, 3, 2401, 5, 4, 7, 49, 31213, 9604, 6, 1, 8, 2, 3, 10, 5, 4, 7, 33, 22 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

In the table output, one can observe constant diagonals (or lines in the square output). The indices of these are: 1, 3, 4, 6, 7, 8, 12, 13, ... (see A002191). And the corresponding values are: 1, 2, 3, 5, 4, 7, 6, 9, ... (see A002192). - Michel Marcus, Dec 19 2013

LINKS

Table of n, a(n) for n=1..88.

FORMULA

Min{x; Mod[sigma[x], n]=r}, r=1..n, n=1, ...

EXAMPLE

Triangle begins

1;

1,3;

1,7,2;

1,5,2,3;

1,4,2,3,8; ...

MATHEMATICA

{k=0, s=0, fl=1}; Table[Print["#"]; Table[fl=1; Print[{r, m}]; Do[s=Mod[DivisorSigma[1, n], m]; If[(s==r)&&(fl==1), Print[n]; fl=0], {n, 1, 150000}], {r, 0, m-1}], {m, 1, 25}]

CROSSREFS

Cf. A000203, A028982, A074384, A074386, A072461, A072462, A072862.

Sequence in context: A146217 A146007 A061782 * A284877 A169659 A091724

Adjacent sequences:  A074622 A074623 A074624 * A074626 A074627 A074628

KEYWORD

nonn,tabl

AUTHOR

Labos Elemer, Aug 26 2002

STATUS

approved

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Last modified May 21 11:19 EDT 2019. Contains 323443 sequences. (Running on oeis4.)