A116285 Numbers k such that k * (k+1) is the concatenation of a number m with itself.
363, 637, 714, 923, 8905, 81818, 336633, 663367, 7272727, 76470589, 333666333, 405436668, 428571429, 447710185, 454545454, 473684211, 526315789, 545454546, 552289815, 571428571, 594563332, 666333667, 692307693, 711446449, 762237762, 834008097, 859982123, 879120879, 902255640, 974025975, 980861244
Offset: 1
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
q:= proc(d,m) local R,t,a,b,x,q; t:= 10^d+1; R:= NULL; for a in numtheory:-divisors(t) do b:= t/a; if igcd(a,b) > 1 then next fi; for x from chrem([0,-m],[a,b]) by t do q:= x*(x+m)/t; if q >= 10^d then break fi; if q >= 10^(d-1) then R:= R, x fi; od od; sort(convert({R},list)); end proc: seq(op(q(d,1)),d=1..10); # Robert Israel, Apr 08 2025
Formula
A161356(n) = a(n)*(a(n)+1). - Michael S. Branicky, Jul 11 2025
Extensions
More terms from Robert Israel, Apr 08 2025
Comments