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 A116300 n times n+9 gives the concatenation of two numbers m and m+1. 5
 26, 66, 3416102887775247376839416334668635, 3756559953325598880263233435801764, 4313503800489302411917772257282208 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..28 EXAMPLE 66 * 75 = 49//50, where // denotes concatenation. MAPLE F:= proc(d) local t, g, Cands: t:= 10^d+1; if NumberTheory:-QuadraticResidue(85, t) <> 1 then return NULL fi; Cands:= map(s -> rhs(op(s)), [msolve(x^2 + 9*x - 1, t)]); g:= proc(r) local v; v:= r^2 + 9*r - 1; v >= t*(t-11)/10 and v < t*(t-2) end proc; op(sort(select(g, Cands))); end proc: map map(F, [\$1..82]); # Robert Israel, Aug 25 2023 CROSSREFS Cf. A116169, A116293, A116299, A116306. Sequence in context: A020155 A063304 A199849 * A299798 A039377 A043200 Adjacent sequences: A116297 A116298 A116299 * A116301 A116302 A116303 KEYWORD nonn,base AUTHOR Giovanni Resta, Feb 06 2006 STATUS approved

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Last modified September 25 14:41 EDT 2023. Contains 365648 sequences. (Running on oeis4.)