A248818 - OEIS

%I #14 May 29 2016 07:05:07

%S 3,20,39,119,224,351,799,879,1076,1504,4064,6879,7999,56847,169640,

%T 346879,470975,893520,1955776,7546879,17604064,36722175,79999999,

%U 95546879,222503984,580483743,584057247,626394816,7999999999,17194139104

%N Numbers n such that the digits of antisigma(n) end in phi(n).

%C Similar to A024816 but using antisigma(n) instead of sigma(n).

%C All the semiprimes of the form 8*10^k-1 are terms. - _Giovanni Resta_, May 29 2016

%e Antisigma of 879 is (879 * 880) / 2 - sigma(879) = 386760 - 1176 = 385584 and phi(879) = 584.

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

%p for n from 1 to q do then a:=ilog10(phi(n))+1;

%p if phi(n)=((n*(n+1)/2-sigma(n)) mod 10^a) then print(n);

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

%Y Cf. A000010, A024816.

%K nonn,base

%O 1,1

%A _Paolo P. Lava_, Oct 15 2014

%E a(18)-a(30) from _Giovanni Resta_, May 29 2016