A365473 Odd semiprimes p*q such that A000120(p)*A000120(q) = A000120(p*q).
15, 51, 85, 95, 111, 119, 123, 187, 219, 221, 335, 365, 411, 447, 485, 511, 629, 655, 685, 697, 771, 831, 879, 959, 965, 1011, 1139, 1241, 1285, 1405, 1535, 1563, 1649, 1731, 1779, 1799, 1923, 1983, 2005, 2019, 2031, 2045, 2227, 2605, 2735, 2815, 2827, 2885, 3099, 3183, 3279, 3281, 3291, 3327
Offset: 1
Examples
a(3) = 85 is a term because 85 = 5 * 17 is an odd semiprime with A000120(5) * A000120(17) = 2 * 2 = 4 = A000120(85).
Links
- Robert Israel, Table of n, a(n) for n = 1..7230
Crossrefs
Programs
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Maple
g:= proc(n) convert(convert(n,base,2),`+`) end proc: N:= 10^4: # for terms <= N S:= NULL: p:= 2: while 3*p <= N do p:= nextprime(p); t:= g(p); q:= 2: do q:= nextprime(q); if q = p or q*p > N then break fi; if g(q)*t = g(p*q) then S:= S, p*q fi; od od: sort([S]);
Comments