A039928 - OEIS

%I #18 Dec 25 2022 19:57:53

%S 0,3,3,0,10,12,1,24,25,32,116,12,412,109,126,2389,12497,28772,126,

%T 72795,247786,770213,159378001963452599318,2169128,442,311,378,789,

%U 10015050,75,74253544,7881195,2461717833658872781238383813854943728,51,17,824,855,2,29981,3087,215308,123456790123456790123456790123456790123452,132813776,1086162642,1836311902,400276874544

%N Sum of first n terms of A_n (using absolute values of terms).

%C Since the sequences in the OEIS occasionally change their initial terms (for editorial reasons), this is an especially ill-defined sequence! - _N. J. A. Sloane_, Jan 01 2005

%C The next term, a(47), is currently unknown. - _Jianing Song_, Oct 07 2018

%H <a href="/index/Se#selfies">Index entries for sequences whose definition involves A_n (or An)</a>.

%e A000001 (Number of groups of order n) begins 0,... -> a(1) = 0

%e A000002 (Kolakoski sequence) begins 1, 2,... -> a(2) = 3

%e A000003 begins 1, 1, 1,... -> a(3) = 3

%e A000004 (The zero sequence) begins 0, 0, 0, 0,... -> a(4) = 0

%e A000005 (The number of divisors) begins 1, 2, 2, 3, 2, ... -> a(5) = 10

%e ...

%e A000010 (Euler totient function) begins 1, 1, 2, 2, 4, 2, 6, 4, 6, ... so a(10) = 1 + 1 + 2 + 2 + 4 + 2 + 6 + 4 + 6 + 4 = 32.

%Y Cf. A031135, A031214, A100543 (uses signed values).

%K dumb,easy,nonn

%O 1,2

%A _Russ Cox_

%E Corrected and extended by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 27 2004

%E a(1) changed from 1 to 0 and extended by _Jianing Song_, Oct 06 2018