A391859 - OEIS

%I #6 Dec 21 2025 22:31:55

%S 1,3,5,7,31,33,51,63,65,93,95,125,127,129,133,161,191,253,255,257,261,

%T 321,381,383,387,509,511,513,517,641,645,765,767,771,775,819,899,1021,

%U 1023,1025,1029,1057,1281,1285,1533,1535,1539,1543,1795,1799,2045,2047,2049,2053,2081,2113,2561,2565,3069,3071,3075

%N Odd numbers k such that 25*k = A048720(m, k) for some m, where A048720 is carryless base-2 multiplication.

%H Antti Karttunen, <a href="/A391859/b391859.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Con#CongruCrossDomain">Index entries for sequences defined by congruent products between domains N and GF(2)[X]</a>.

%H <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.

%H <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>.

%F {Odd k such that A280500(25*k, k) = m for some m > 0}.

%e See examples in A391858.

%o (PARI) is_A391859(k) = ((k%2) && (0==lift(Pol(binary(25*k)*Mod(1, 2)) % Pol(binary(k))*Mod(1, 2))));

%Y Row 25 of A391725. Odd terms of A391858.

%Y Cf. A048720, A280500.

%Y Cf. also A391745, A391861.

%K nonn,base

%O 1,2

%A _Antti Karttunen_, Dec 21 2025