This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A080463 #15 Jan 11 2016 03:22:10 %S A080463 0,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,10,2,3,4,5,6,7,8,9,10,11,3,4,5, %T A080463 6,7,8,9,10,11,12,4,5,6,7,8,9,10,11,12,13,5,6,7,8,9,10,11,12,13,14,6, %U A080463 7,8,9,10,11,12,13,14,15,7,8,9,10,11,12,13,14,15,16,8,9,10,11,12,13,14,15,16 %N A080463 Sum of the two numbers formed by alternate digits of n. %C A080463 First 99 terms match with those of A007953. %C A080463 They also match A209685. - _M. F. Hasler_, Jan 10 2016 %H A080463 M. F. Hasler, <a href="/A080463/b080463.txt">Table of n, a(n) for n = 0..10000</a> %F A080463 From _Robert Israel_, Jan 10 2016: (Start) %F A080463 f(n) = n mod 10 + floor(n/10) mod 10 + 10*f(floor(n/100)). %F A080463 G.f. G(x) satisfies G(x) = (x + 2x^2 + ... + 9x^9)/(1-x^10) + (x^10 + 2 x^20 + ... + 9 x^90)/((1-x)(1+x^10+...+x^90) + 10 (1 + x + ... + x^99) G(x^10). %F A080463 (End) %e A080463 a(132546) = 124 + 356 = 480. %p A080463 f:= proc(n) option remember; n mod 10 + (floor(n/10) mod 10) + 10*procname(floor(n/100)) end proc: %p A080463 f(0):= 0: %p A080463 seq(f(n),n=0..1000); # _Robert Israel_, Jan 10 2016 %o A080463 (PARI) A080463(n)=abs(vector(#n=digits(n),j,10^((#n-j)\2))*n~) \\ _M. F. Hasler_, Jan 10 2016 %Y A080463 Cf. A007953, A080464, A080465. %K A080463 base,easy,nonn,look %O A080463 0,3 %A A080463 _Amarnath Murthy_, Mar 02 2003 %E A080463 More terms from _Ray Chandler_, Oct 11 2003 %E A080463 Extended to offset 0 and b-file by _M. F. Hasler_, Jan 10 2016