A305670 Numbers k not ending in zero that are a substring of k*(k+1).

9, 99, 146, 999, 3701, 8881, 9999, 10512, 13088, 13271, 13466, 15625, 49547, 50502, 60146, 73398, 85941, 99999, 155613, 205062, 513335, 712539, 999999, 1005012, 1060146, 1334666, 3990487, 5005002, 9999999, 20050062, 26930824, 39341318, 46022544, 58331666, 63116013

Offset

1,1

Comments

A002283 is a subset of this sequence.

Contains 5*10^(2*m)+5*10^m+2 and 2*10^(2*m+1)+5*10^(m+1)+62 for m >= 2. - Robert Israel, Jun 29 2018

Links

Giovanni Resta, Table of n, a(n) for n = 1..90

Example

13088 * 13089 = 171308832;
13271 * 13272 = 176132712.

Maple

P:=proc(q) local k, n; for n from 1 to q do if n mod 10>0 then
for k from 1 to ilog10(n*(n+1))-ilog10(n)+1 do
if n=trunc(n*(n+1)/10^(k-1)) mod 10^(ilog10(n)+1) then print(n);
break; fi; od; fi; od; end: P(10^8);

Crossrefs

Cf. A002283, A316263.

Sequence in context: A306567 A061817 A083835 * A045644 A116136 A139280

Adjacent sequences: A305667 A305668 A305669 * A305671 A305672 A305673

Keyword

nonn,base

Author

Paolo P. Lava, Jun 28 2018

Extensions

Edited by Robert Israel, Jun 29 2018

Status

approved