This site is supported by donations to The OEIS Foundation.

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A207359 Indices n, not squarefree, where A055231(n) = A055231(n-A055231(n)). 0

%I

%S 9,45,63,99,117,153,171,207,261,279,289,315,333,369,387,423,477,495,

%T 531,549,585,603,639,657,676,693,711,747,765,801,819,855,873,909,927,

%U 963,981,1017,1035,1071,1143,1179,1197,1233,1251,1287,1305,1341,1359,1395

%N Indices n, not squarefree, where A055231(n) = A055231(n-A055231(n)).

%C A055231(n) is the powerfree part of n. This sequence is infinite because all numbers of the form n = 9p, where p is a prime > 3, are in the sequence : A055231(9p) = p and A055231(9p - p) = A055231(8p) = p. The positive numbers of A055792 are also in the sequence because A055792(n) are squares and A055792(n)-1 are also squares.

%e 63 is in the sequence because A055231(63) = A055231(7*3^2) = 7, A055231(63 - 7) = A055231(56) = A055231(7*2^3) = 7.

%p isA013929 := proc(n)

%p n>3 and not numtheory[issqrfree](n) ;

%p end proc:

%p isA207359 := proc(n)

%p isA013929(n) and (A055231(n)- A055231(n- A055231(n))=0);

%p end proc:

%p for n from 1 to 5000 do

%p if isA207359(n) then

%p printf(`%d, `,n);

%p end if;

%p end do: # adapted from A140394.

%Y Cf. A055231, A140394.

%K nonn

%O 1,1

%A _Michel Lagneau_, Feb 17 2012

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.