A249065 Numbers n such that n = concatenate(a, b) and sigma(a) + sigma(b) = phi(n).

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

Offset: 1

Author

Paolo P. Lava, Oct 20 2014

Keywords

• nonn
• base

Examples

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

Crossrefs

Cf. A000005, A000203, A239562.

Programs

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);