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!)
A038838 Numbers that are divisible by the square of an odd prime. 9
9, 18, 25, 27, 36, 45, 49, 50, 54, 63, 72, 75, 81, 90, 98, 99, 100, 108, 117, 121, 125, 126, 135, 144, 147, 150, 153, 162, 169, 171, 175, 180, 189, 196, 198, 200, 207, 216, 225, 234, 242, 243, 245, 250, 252, 261, 270, 275, 279, 288, 289, 294, 297, 300, 306 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Condition 1 of Theorem 7.5 (Robinson, 1979) includes: "k is a multiple of a square of an odd prime." - Jonathan Vos Post, Aug 06 2007

Subsequence of A167662. - Reinhard Zumkeller, Nov 08 2009

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..10000

Beeler, M., Gosper, R. W. and Schroeppel, R., HAKMEM ITEM 45

R. M. Robinson, Multiple tiling of n-dimensional space by unit cubes, Math. Z. 166 (1979), 225-264.

Chuanming Zong, What is known about unit cubes, Bull. Amer. Math. Soc. 42 (2005), 181-211; Robinson theorem cited on p. 204.

FORMULA

{a(n)} = {j such that for some k>1 A001248(k)|j} = {j such that for some k>0 (A065091(k)^2)|j}. - Jonathan Vos Post, Aug 06 2007

A008966(A000265(a(n))) = 0. - Reinhard Zumkeller, Nov 08 2009

PROG

(PARI) {a(n) = my(m, c); if( n<1, 0, c=0; m=0; while( c<n, m++; if( moebius(m / 2^valuation(m, 2))==0, c++)); m)}; /* Michael Somos, Aug 22 2006 */

(PARI) list(lim)=my(v=List(), n, e, t); forfactored(k=9, lim\1, e=k[2][, 2]; t=#e; n=k[1]; if(if(n%2 && t, vecmax(e)>1, t>1, vecmax(e[2..t])>1, 0), listput(v, k[1]))); Vec(v) \\ Charles R Greathouse IV, Jan 08 2018

CROSSREFS

Cf. A000040, A001248, A065091, A122132 (complement).

Intersection of A013929 (nonsquarefrees) and A061345 (odd prime powers).

Sequence in context: A015798 A028494 A167663 * A038837 A325359 A307579

Adjacent sequences:  A038835 A038836 A038837 * A038839 A038840 A038841

KEYWORD

nonn

AUTHOR

David W. Wilson

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 5 18:48 EDT 2020. Contains 334854 sequences. (Running on oeis4.)