login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A295880 Filter combining the number of divisors (A000005) and the sum of divisors (A000203) of n. 3
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 44, 49, 50, 51, 44, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 57, 61, 64, 65, 66, 67, 68, 69, 57, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 79 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

Restricted growth sequence transform of a(n) = (1/2)*(2 + ((A000005(n) + A000203(n))^2) - A000005(n) - 3*A000203(n)).

PROG

(PARI)

allocatemem(2^30);

up_to = 65537;

rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om, invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om, invec[i], i); outvec[i] = u; u++ )); outvec; };

write_to_bfile(start_offset, vec, bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }

A000005(n) = numdiv(n);

A000203(n) = sigma(n);

Anotsubmitted0(n) = (1/2)*(2 + ((A000005(n)+A000203(n))^2) - A000005(n) - 3*A000203(n));

write_to_bfile(1, rgs_transform(vector(up_to, n, Anotsubmitted0(n))), "b295880.txt");

CROSSREFS

Cf. A000005, A000203, A295300, A295888.

Sequence in context: A293704 A322021 A295888 * A296090 A323372 A295300

Adjacent sequences:  A295877 A295878 A295879 * A295881 A295882 A295883

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 03 2017

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 26 08:09 EDT 2020. Contains 337346 sequences. (Running on oeis4.)