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

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A033457 GCD-convolution of squares A000290 with themselves. 2
1, 2, 6, 4, 19, 6, 28, 24, 45, 10, 98, 12, 79, 94, 120, 16, 201, 18, 238, 164, 171, 22, 436, 120, 229, 234, 426, 28, 695, 30, 496, 352, 369, 370, 1014, 36, 451, 470, 1068, 40, 1261, 42, 946, 1020, 639, 46, 1832, 336 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Danny Rorabaugh, Table of n, a(n) for n = 0..10000

FORMULA

a(n-2) = Sum_{d|n, d<n} d^2*phi(n/d). - Vladeta Jovovic, Aug 27 2003

MATHEMATICA

Table[Sum[d^2*EulerPhi[(n + 2)/d], {d, Most@ Divisors[n + 2]}], {n, 0, 47}] (* Michael De Vlieger, Mar 20 2015 *)

PROG

(Sage) sum([d^2*euler_phi(int((n+2)/d)) for d in range(1, n+2) if (n+2)%d==0]) # Danny Rorabaugh, Mar 20 2015

CROSSREFS

Cf. A069097.

Sequence in context: A098917 A054786 A269372 * A133936 A065350 A063427

Adjacent sequences:  A033454 A033455 A033456 * A033458 A033459 A033460

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 4 15:05 EST 2016. Contains 278750 sequences.