cp's OEIS Frontend

A207359 Indices n, not squarefree, where A055231(n) = A055231(n-A055231(n)).

%I A207359 #16 Jan 09 2013 15:18:13
%S A207359 9,45,63,99,117,153,171,207,261,279,289,315,333,369,387,423,477,495,
%T A207359 531,549,585,603,639,657,676,693,711,747,765,801,819,855,873,909,927,
%U A207359 963,981,1017,1035,1071,1143,1179,1197,1233,1251,1287,1305,1341,1359,1395
%N A207359 Indices n, not squarefree, where A055231(n) = A055231(n-A055231(n)).
%C A207359 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 A207359 63 is in the sequence because A055231(63) = A055231(7*3^2) = 7, A055231(63 - 7) = A055231(56) = A055231(7*2^3) = 7.
%p A207359 isA013929 := proc(n)
%p A207359     n>3 and not numtheory[issqrfree](n) ;
%p A207359 end proc:
%p A207359 isA207359 := proc(n)
%p A207359     isA013929(n) and (A055231(n)- A055231(n- A055231(n))=0);
%p A207359 end proc:
%p A207359 for n from 1 to 5000 do
%p A207359       if isA207359(n) then
%p A207359           printf(`%d, `,n);
%p A207359       end if;
%p A207359 end do: #  adapted from A140394.
%Y A207359 Cf. A055231, A140394.
%K A207359 nonn
%O A207359 1,1
%A A207359 _Michel Lagneau_, Feb 17 2012