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A182081 Next semiprime after the partial sum of the first n semiprimes. 1

%I #10 Apr 10 2012 22:32:27

%S 6,14,21,33,46,62,82,106,129,155,187,221,259,295,334,381,427,478,533,

%T 591,649,713,778,849,921,995,1077,1165,1253,1337,1437,1522,1618,1711,

%U 1814,1927,2041,2159,2279,2402,2533,2643,2773,2906,3039,3183,3326,3466,3611

%N Next semiprime after the partial sum of the first n semiprimes.

%C This is to A202301 next prime after the partial sum of the first n primes as A001358 semiprimes is to A000040 primes.

%H Alois P. Heinz, <a href="/A182081/b182081.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = min { k > A062198(n) and k in A001358 }.

%e a(10) = 155 because 4 + 6 + 9 + 10 + 14 + 15 + 21 + 22 + 25 + 26 = 152, and the next semiprime after 152 is 155.

%p h:= proc(m) local k;

%p for k from m+1 while isprime(k) or

%p add (i[2], i=ifactors(k)[2])<>2 do od; k

%p end:

%p b:= proc(n)

%p b(n):= h(b(n-1))

%p end: b(0):=0:

%p s:= proc(n)

%p s(n):= b(n) +s(n-1)

%p end: s(0):=0:

%p a:= n-> h(s(n)):

%p seq (a(n), n=1..60); # _Alois P. Heinz_, Apr 10 2012

%Y Cf. A001358, A062198, A202301.

%K nonn,easy

%O 1,1

%A _Jonathan Vos Post_, Apr 10 2012

%E More terms from _Alois P. Heinz_, Apr 10 2012

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Last modified April 25 05:49 EDT 2024. Contains 371964 sequences. (Running on oeis4.)