A116167 Numbers k such that k concatenated with k+1 gives the product of two numbers which differ by 7.

7, 493, 607, 629, 757, 17927, 33247, 93869, 19467217, 31223879, 72757727, 13454739732766891651472740499, 40093333713615672956030023507, 48089152118689474641229584727, 66424317743191484432891678269

Offset

1,1

Comments

If k+1 has d digits, the concatenation is k//k+1 = 10^d*k+k+1 = m*(m+7), therefore k//k-7 = 10^d*k+k-7 = (m-1)*(m+8), so there is a large overlap with A116114. - R. J. Mathar, May 22 2026

Links

Table of n, a(n) for n=1..15.

Example

72757727//72757728 = 85298137 * 85298144, where // denotes concatenation.

Crossrefs

Cf. A116160, A115428, A116168, A116180, A116298.

Sequence in context: A119621 A142734 A120773 * A296175 A319831 A122523

Adjacent sequences: A116164 A116165 A116166 * A116168 A116169 A116170

Keyword

nonn,base,changed

Author

Giovanni Resta, Feb 06 2006

Status

approved