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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
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
Sequence in context: A020155 A063304 A199849 * A299798 A039377 A043200
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
STATUS
approved

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Last modified March 28 15:28 EDT 2024. Contains 371254 sequences. (Running on oeis4.)