cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A157941 Numbers n divisible by the largest prime < sqrt(n), A007917(A000196(n-1)).

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%I A157941 #10 Jul 25 2024 14:08:47
%S A157941 6,8,12,15,18,21,24,30,35,40,45,56,63,70,77,84,91,98,105,112,119,132,
%T A157941 143,154,165,182,195,208,221,234,247,260,273,286,306,323,340,357,380,
%U A157941 399,418,437,456,475,494,513,552,575,598,621,644,667,690,713,736,759
%N A157941 Numbers n divisible by the largest prime < sqrt(n), A007917(A000196(n-1)).
%C A157941 Includes products of pairs of consecutive primes (A006094) as subsequence, equals A157942 with squares of primes (A001248) removed.
%C A157941 For a number < 5 the definition does not make much sense, since there is no prime < sqrt(4) = 2, so we don't consider them here.
%H A157941 Harvey P. Dale, <a href="/A157941/b157941.txt">Table of n, a(n) for n = 1..1000</a>
%t A157941 Select[Range[6,800],Divisible[#,NextPrime[Sqrt[#],-1]]&] (* _Harvey P. Dale_, Sep 14 2019 *)
%o A157941 (PARI) for( n=5,999, n % precprime(sqrtint(n-1)) || print1(n","))
%K A157941 nonn
%O A157941 1,1
%A A157941 _M. F. Hasler_, Mar 09 2009