A116120 Numbers k such that k concatenated with k-5 gives the product of two numbers which differ by 1.

7, 55, 5255, 6295, 75511, 92137, 5551405, 7943911, 1257669432489239675, 2148743977942130765, 2877834685014859837, 4164942361780146967, 10235898967817894552965, 15389481849681116007757

Offset

1,1

Comments

If k-5 has d digits, the concatenation is k//k-5 = 10^d*k+k-5 = m*(m+1), therefore k//k-7 = 10^d*k+k-7 = (m-1)*(m+2), so there is a large overlap with A116110. - R. J. Mathar, May 22 2026

Links

Table of n, a(n) for n=1..14.

Crossrefs

Cf. A116115, A116121, A116134, A116251.

Sequence in context: A305282 A197228 A009521 * A056719 A038855 A097254

Adjacent sequences: A116117 A116118 A116119 * A116121 A116122 A116123

Keyword

nonn,base,changed

Author

Giovanni Resta, Feb 06 2006

Status

approved