A368993 - OEIS

%I #7 Jan 11 2024 20:04:55

%S 1,2,3,4,5,6,7,8,9,9,9,10,11,12,13,14,15,16,16,17,17,17,18,19,20,21,

%T 22,23,24,25,26,27,28,28,28,29,29,29,30,30,30,30,30,30,31,31,31,32,33,

%U 33,34,35,35,36,37,38,39,39,39,40,41,42,43,44,45,46,46,47,47,47,48,49,49,49,49,49,50,51,51,52,52,52

%N Doudna-gram for A336547; Partial sums of A368992.

%H Antti Karttunen, <a href="/A368993/b368993.txt">Table of n, a(n) for n = 0..65537</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(0) = 0, and for n > 0, a(n) = a(n-1) + A368992(n).

%o (PARI)

%o up_to = 65537;

%o A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); (t); };

%o A336546(n) = { my(f=factor(n)); (sigma(n)==lcm(vector(#f~,k,sigma(f[k,1]^f[k,2])))); };

%o A368992(n) = A336546(A005940(1+n));

%o A368993list(up_to) = { my(v=vector(up_to), s=A368992(0)); for(i=1, up_to, s += A368992(i); v[i] = s); (v); };

%o v368993 = A368993list(up_to);

%o A368993(n) = if(!n, A368992(0), v368993[n]);

%Y Partial sums of A368992.

%Y Cf. A005940, A324054, A336546, A336547.

%Y Cf. also A368910, A368991.

%K nonn

%O 0,2

%A _Antti Karttunen_, Jan 11 2024