login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A291750 Compound filter: a(n) = P(A003557(n), A048250(n)), where P(n,k) is sequence A000027 used as a pairing function. 17
1, 4, 7, 8, 16, 67, 29, 19, 18, 154, 67, 80, 92, 277, 277, 53, 154, 94, 191, 173, 497, 631, 277, 109, 50, 862, 75, 302, 436, 2557, 497, 169, 1129, 1432, 1129, 142, 704, 1771, 1541, 214, 862, 4561, 947, 668, 328, 2557, 1129, 179, 98, 236, 2557, 905, 1432, 199, 2557, 355, 3161, 4006, 1771, 2630, 1892, 4561, 564, 593, 3487, 10297, 2279, 1487, 4561, 10297, 2557 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A000203 (sigma(n)) is a function of this sequence, because formula

  A000203(n) = A092261(n) * A295294(n)

can be rewritten as a relation:

  A000203(n) = A000203(A057521(n)) * A048250(n) / A048250(A057521(n)),

where A057521(n) = A064549(A003557(n)), thus A000203(n) is a function of A003557(n) and A048250(n), the values that are packed here into a(n).

A001615 (Dedekind's psi) is a function of this sequence, because it can be written as A001615(n) = A003557(n)*A048250(n).

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (1/2)*(2 + ((A003557(n) + A048250(n))^2) - A003557(n) - 3*A048250(n)).

PROG

(PARI)

A003557(n) = n/factorback(factor(n)[, 1]); \\ This function from Charles R Greathouse IV, Nov 17 2014

A048250(n) = if(n<1, 0, sumdiv(n, d, if(core(d)==d, d)));

A291750(n) = (1/2)*(2 + ((A003557(n)+A048250(n))^2) - A003557(n) - 3*A048250(n));

CROSSREFS

Cf. A000027, A000203, A001615, A003557, A048250, A291751 (rgs-version of this filter).

Sequence in context: A051219 A270216 A237599 * A007285 A225430 A295325

Adjacent sequences:  A291747 A291748 A291749 * A291751 A291752 A291753

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 04 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 November 16 19:17 EST 2019. Contains 329201 sequences. (Running on oeis4.)