cp's OEIS Frontend

A372290 Numbers that occur in the odd bisection of A371094.

%I A372290 #12 Apr 26 2024 10:59:21
%S A372290 21,45,69,93,117,141,165,189,213,237,261,285,309,333,341,357,381,405,
%T A372290 429,453,477,501,525,549,573,597,621,645,669,693,717,725,741,765,789,
%U A372290 813,837,861,885,909,933,957,981,1005,1029,1053,1077,1101,1109,1125,1149,1173,1197,1221,1245,1269,1293,1317,1341,1365,1389
%N A372290 Numbers that occur in the odd bisection of A371094.
%C A372290 Numbers that occur in array A371100.
%H A372290 Antti Karttunen, <a href="/A372290/b372290.txt">Table of n, a(n) for n = 1..62122</a>
%e A372290 21 is present because A371094(1) = A371094(3) = 21.
%e A372290 45 is present because A371094(7) = 45.
%e A372290 87381 is present because A371094(85) = A371094(213) = A371094(7281) = A371094(14563) = 87381.
%o A372290 (PARI)
%o A372290 A371094(n) = { my(m=1+3*n, e=valuation(m,2)); ((m*(2^e)) + (((4^e)-1)/3)); };
%o A372290 isA372290(n) = if(!(n%2),0,forstep(k=1,n,2,if(A371094(k)==n,return(1))); (0));
%o A372290 (PARI)
%o A372290 A371094(n) = { my(m=1+3*n, e=valuation(m,2)); ((m*(2^e)) + (((4^e)-1)/3)); };
%o A372290 A372290list(up_to_n) = { my(v=vector((1+up_to_n)/2), x, lista=List([])); forstep(k=1,up_to_n,2,x=A371094(k); if(x <= up_to_n, v[(x+1)/2]++)); for(i=1,(1+up_to_n)/2,if(v[i]>0, listput(lista,i+i-1))); Vec(lista); };
%Y A372290 Union of A372291 and A372292.
%Y A372290 Cf. A102603 (subsequence), A371094, A371100.
%K A372290 nonn
%O A372290 1,1
%A A372290 _Antti Karttunen_, Apr 26 2024