A280967 -id:A280967 - cp's OEIS frontend

A280972 Numbers that appear in both A278909 and A280967 but not in A280971.

765, 1275, 1467, 1503, 1515, 1695, 2910, 2975, 3066, 3423, 4335, 4539, 4605, 4862, 4923, 4947, 4975, 5110, 5295, 5335, 5375, 5559, 5787, 5790, 5835, 5885, 6069, 6123, 6495, 6735, 6783, 7035, 7134, 9195, 9567, 9583, 9645, 9819, 9915, 10087, 10155, 10218, 10234, 10491, 10686, 10959, 10983, 11211

Offset: 1

Ely Golden, Jan 11 2017

Binary equivalent of the sequence representing Numbers that appear in both A176670 and A020342 but not A280928 (currently no members are known).

			765 = A278909(41) = A280967(32) but is not present in A280971.

Ely Golden, Table of n, a(n) for n = 1..896

Cf. A278909, A280967, A280971.

A280971 Composite numbers having the same bits as their prime factors (with multiplicity), including zero bits.

Original entry on oeis.org

159, 287, 303, 319, 591, 623, 679, 687, 699, 763, 1135, 1167, 1203, 1243, 1247, 1271, 1351, 1371, 1391, 1631, 2167, 2173, 2231, 2285, 2319, 2359, 2463, 2471, 2495, 2519, 2743, 2779, 2787, 2809, 2863, 2931, 2933, 2991, 3029, 3039, 3503, 4223, 4279, 4287, 4319, 4343, 4411, 4439, 4479, 4487

Offset: 1

Ely Golden, Jan 11 2017

Binary equivalent of A280928.

Subsequence of A278909 as well as A280967. The terms in A278909 and A280967 but not this sequence are given by A280972.

Ely Golden, Table of n, a(n) for n = 1..10000

Cf. A278909, A280967, A280928.

from sympy import factorint
def ok(n):
    f = factorint(n)
    return sum(f.values()) > 1 and sorted(bin(n)[2:]) == sorted("".join(bin(p)[2:]*f[p] for p in f))
print([k for k in range(5000) if ok(k)]) # Michael S. Branicky, Apr 20 2025

def factorbits(x):
    if(x<2):
        return (0,0);
    s=0;t=0
    f=list(factor(x));
    #ensures inequality of numfactorbits(x) and bin(x).count("1") if x is prime
    if((len(f)==1)&(f[0][1]==1)):
        return (0,0);
    for c in range(len(f)):
        s+=bin(f[c][0]).count("1")*f[c][1]
        t+=(bin(f[c][0]).count("0")-1)*f[c][1]
    return (s,t);
counter=2
index=1
while(index<=10000):
    if(factorbits(counter)==(bin(counter).count("1"),bin(counter).count("0")-1)):
        print(str(index)+" "+str(counter))
        index+=1;
    counter+=1;

cp's OEIS Frontend

A280972 Numbers that appear in both A278909 and A280967 but not in A280971.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs