A357651 Sliding numbers which are products of two distinct primes.

65, 133, 205, 254, 502, 785, 2005, 10001, 15689, 16265, 20005, 31282, 79405, 100001, 156314, 390881, 1000001, 3906506, 10000001, 100000001, 244144721, 5000000002, 6103532009, 152587956161, 762939584197, 3814699887065, 19073486852413, 38146972918394, 200000000000005, 10000000000000000001

Offset

1,1

Comments

A squarefree subsequence of numbers of the form p + q where 1/p + 1/q = (p + q)/10^k for some k >= 1.

Links

Table of n, a(n) for n=1..30.

Example

65 = 5*13 (65 = 25 + 40 and 1/25 + 1/40 = 0.065).
133 = 7*19 (133 = 8 + 125 and 1/8 + 1/125 = 0.133).
15689 = 29*541 (15689 = 64 + 15625 and 1/64 + 1/15625 = 0.015689).
244144721 = 641*3808814096 (244144721 = 4096 + 244140625 and 1/4096 + 1/244140625 = 0.000244144721).

Crossrefs

Intersection of A103182 and A006881.

Sequence in context: A352982 A355543 A348759 * A294169 A073631 A285300

Adjacent sequences: A357648 A357649 A357650 * A357652 A357653 A357654

Keyword

nonn,base

Author

Massimo Kofler, Oct 07 2022

Extensions

More terms from Hugo Pfoertner, Oct 08 2022

Status

approved