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 A332860 a(n) is the least prime p such that p+prime(n) has exactly n prime factors, counted with multiplicity. 1
 3, 3, 3, 17, 37, 83, 271, 557, 1129, 2531, 2017, 21467, 28631, 24533, 73681, 98251, 196549, 589763, 524221, 2621369, 5242807, 14155697, 69205933, 16777127, 83885983, 67108763, 1543503769, 1006632853, 1342177171, 3623878543, 11811159937, 54358179709, 32212254583, 225485782901, 260919263083 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..400 FORMULA A001222(a(n)+A000040(n)) = n. EXAMPLE a(4) = 17 because 17 is prime and 17 + prime(4) = 17 + 7 = 24 = 2^3*3 has 4 prime factors counted with multiplicity, and no smaller prime works. MAPLE g:= proc(n, N, pmax) local Res, k, p; if n = 0 then return [[]] fi; Res:= NULL; p:=1; do p:= nextprime(p); if p >= pmax or 2^(n-1)*p > N then return [Res] fi; for k from 1 to n while 2^(n-k)*p^k <= N do Res:= Res, op(map(t -> [op(t), p\$k], procname(n-k, N/p^k, p))); od; od; end proc: h:= (n, N) -> sort(map(convert, g(n, N, N/2^(n-1)+1), `*`)): f:= proc(n) local pn, N, lastN, R, r; pn:= ithprime(n); N:= 2^n-1; do lastN:= N; N:= 2*N; R:= select(`>`, h(n, N), lastN); for r in R do if r > pn and isprime(r-pn) then return r-pn fi od; od; end proc: map(f, [\$1..50]); CROSSREFS Cf. A000040, A001222. Sequence in context: A290159 A356388 A083562 * A106542 A342363 A229934 Adjacent sequences: A332857 A332858 A332859 * A332861 A332862 A332863 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Mar 10 2020 STATUS approved

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Last modified August 4 13:44 EDT 2024. Contains 374923 sequences. (Running on oeis4.)