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A249065 Numbers n such that n = concatenate(a, b) and sigma(a) + sigma(b) = phi(n). 1
12, 420, 966, 2700, 5700, 5940, 7440, 12540, 71100, 76680, 107880, 118680, 121920, 156420, 160650, 161880, 259080, 284580, 339150, 353430, 395850, 498420, 585200, 600780, 701220, 746130, 752100, 771420, 870870, 1052220, 1249680, 1654620, 1684020, 1696080 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..34.

EXAMPLE

For n = 966 we can consider 966 as 96 U 6; sigma(96) + sigma(6) = 252 + 12 = 264 = phi(966).

MAPLE

with(numtheory); P:=proc(q) local a, b, i, n; for n from 1 to q do

for i from 1 to ilog10(n) do a:=trunc(n/10^i); b:=n-a*10^i;

if sigma(a)+sigma(b)=phi(n) then print(n); break;

fi; od; od; end: P(10^9);

CROSSREFS

Cf. A000005, A000203, A239562.

Sequence in context: A282883 A163971 A340306 * A098602 A000897 A036687

Adjacent sequences:  A249062 A249063 A249064 * A249066 A249067 A249068

KEYWORD

nonn,base

AUTHOR

Paolo P. Lava, Oct 20 2014

STATUS

approved

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Last modified April 22 14:33 EDT 2021. Contains 343177 sequences. (Running on oeis4.)