cp's OEIS Frontend

A297150 Let b(k) denote A292081(k); the sequence lists numbers b(2n) where for all m > n, b(2m) > b(2n).

%I A297150 #28 Sep 08 2022 08:46:20
%S A297150 35,65,95,115,155,185,215,235,265,305,335,365,395,415,445,485,515,545,
%T A297150 565,635,655,695,755,785,815,835,865,905,965,995,1055,1115,1145,1165,
%U A297150 1205,1255,1285,1315,1355,1385,1415,1465,1535,1565,1585,1655,1685,1745,1765,1795,1835,1865,1895,1915,1945,1985
%N A297150 Let b(k) denote A292081(k); the sequence lists numbers b(2n) where for all m > n, b(2m) > b(2n).
%C A297150 This is also an ascending subsequence of the even-indexed terms of A056240(2n) (of which A292081 is a subsequence). For n >= 1, a(n) is a semiprime of the form a(n)=5*A049591(n), and the index m in A056240 of any term in this sequence belongs to the sequence of even numbers m such that m-5 is prime and m-3 is not prime (A297925). See A297925 for explanation.
%H A297150 Vincenzo Librandi, <a href="/A297150/b297150.txt">Table of n, a(n) for n = 1..1690</a>
%F A297150 a(n) = 5*A049591(n) = A056240(A297925(n)).
%e A297150 a(1)=5*A049591(1)=5*7=35. Also A056240(A297925(1))=A056240(12)=35.
%e A297150 a(17)=5*A049591(17)=5*103=515. Also A056240(A297925(17))=A056240(108)=515.
%t A297150 5 Select[Prime[Range[3, 100]], ! PrimeQ[(# + 2)] &] (* _Vincenzo Librandi_, Nov 12 2018 *)
%o A297150 (Magma) [5*p: p in PrimesInInterval(3, 500) | not IsPrime(p + 2)]; // _Vincenzo Librandi_, Nov 12 2018
%Y A297150 Similar to A288313.
%Y A297150 Cf. A292081, A288313, A056240, A049591, A297925.
%K A297150 nonn
%O A297150 1,1
%A A297150 _David James Sycamore_, Dec 26 2017