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A239244 Let y be the sum of the numbers x coprime to n, with x<=n. Sequence lists n such that digits of y end in 'n'. 1
3, 4, 6, 80, 920, 37568, 56352, 7148453888, 7169453056, 7286124544, 7325797376, 7595232256, 8935567360, 9107655680, 13403351040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n*phi(n)/2 is of the form 'm' U 'n'.

LINKS

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

EXAMPLE

phi(920) = 352; 902*352/2 = 161920 that is '161' U '920'.

MAPLE

with(numtheory); P:=proc(q) local a, b, n;

for n from 1 to q do a:=n; b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od;

if n=((n*phi(n)/2) mod 10^b) then print(n); fi; od; end: P(10^9);

CROSSREFS

Cf. A000010, A239245.

Sequence in context: A019120 A263940 A256326 * A267943 A066466 A332511

Adjacent sequences:  A239241 A239242 A239243 * A239245 A239246 A239247

KEYWORD

nonn,more,base

AUTHOR

Paolo P. Lava, Mar 13 2014

EXTENSIONS

a(8)-a(15) from Giovanni Resta, Mar 14 2014

STATUS

approved

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Last modified July 6 23:01 EDT 2020. Contains 335484 sequences. (Running on oeis4.)