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!)
A296088 Filter combining sigma(n) with the parity of n; restricted growth sequence transform of ((-1)^n)*A000203(n). 2
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 15, 23, 24, 20, 25, 26, 27, 28, 21, 29, 30, 31, 30, 32, 33, 23, 34, 35, 36, 37, 38, 39, 40, 28, 30, 41, 42, 43, 44, 45, 46, 47, 44, 47, 48, 35, 49, 50, 51, 37, 52, 53, 54, 55, 56, 57, 58, 55, 44, 59, 60, 61, 62, 63, 58, 50, 48, 64, 65, 57, 54, 66, 67, 68, 69, 70, 71, 72, 73, 50, 74, 55, 69 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

For n = 21 and 31 the restricted growth sequence transform assigns the same value (we have a(21) = a(31) = 21) because both numbers are odd, and the sum of their divisors is equal as sigma(21) = sigma(31) = 32.

On the other hand, although sigma(14) = sigma(15) = 24, a(14) != a(15) because the other number is even and the other number is odd. Compare to A286603.

PROG

(PARI)

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])); }

write_to_bfile(1, rgs_transform(vector(up_to, n, ((-1)^n)*sigma(n))), "b296088.txt");

CROSSREFS

Cf. A000035, A000203, A286603, A291761, A296089.

Sequence in context: A030066 A192438 A081331 * A296089 A323368 A080686

Adjacent sequences:  A296085 A296086 A296087 * A296089 A296090 A296091

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 07 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 June 2 08:00 EDT 2020. Contains 334767 sequences. (Running on oeis4.)