OFFSET
1,1
COMMENTS
This sequence is a primitive sequence of A000028; it lists minimal terms in that sequence having their prime exponents.
EXAMPLE
180 is a term as 180 = 2^2 * 3^2 * 5 which has exponents in binary 10_2, 10_2 and 1_2 respectively. The sum of binary digits of those exponents is (1 + 0) + (1 + 0) + 1 = 3 which is odd. Furthermore, 180 is a product of primorials; 180 = 30 * 6. Therefore, 180 is in the sequence.
PROG
(PARI) is(n) = {if(n==1, return(0)); my(f = factor(n)); f[#f~, 1] == prime(#f~) && vecsort(f[, 2], , 4) == f[, 2] && sum(i=1, #f~, hammingweight(f[i, 2]))%2}
CROSSREFS
KEYWORD
nonn,base
AUTHOR
David A. Corneth, Mar 20 2019
STATUS
approved