A346641 Numbers k with at least one partition into two parts (s,t), s<=t such that t | s*k but no proper divisor of k has this property.

2, 15, 35, 63, 77, 91, 99, 117, 143, 153, 187, 209, 221, 247, 299, 323, 325, 357, 391, 399, 425, 437, 475, 483, 493, 513, 527, 551, 575, 589, 609, 621, 651, 667, 703, 713, 725, 759, 775, 777, 783, 837, 851, 861, 899, 925, 943, 957, 989, 999, 1023, 1025, 1073, 1075

Offset

1,1

Comments

Primitive subsequence of A350803.

Odd terms form primitive subsequence of A090196. - Bernard Schott, Jan 23 2022

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Example

k = 15 = 6 + 9 = s + t is in the sequence (t = 9 | 6*15 = 90 = s*k) but no proper divisor of 15 has this property.

Prog

(PARI) upto(n) = { my(v = vector(n, i, -1)); for(i = 1, n, if(v[i] == -1, if(isA350803(i), v[i] = 1; for(j = 2, n\i, v[i*j] = 0; ) ) ) ); select(x->x==1, v, 1) }
isA350803(n) = { for(i = 1, n\2, if((n*i)%(n-i) == 0, return(1) ) ); return(0) }

Crossrefs

Cf. A350803.

Subsequence: A082663.

Sequence in context: A300635 A301357 A271909 * A075541 A075542 A064113

Adjacent sequences: A346638 A346639 A346640 * A346642 A346643 A346644

Keyword

nonn

Author

David A. Corneth, Jan 22 2022

Status

approved