|
%I #34 Dec 20 2019 06:44:56
%S 4,6,8,9,44,46,48,49,64,66,68,69,84,86,88,94,96,98,99,444,446,448,464,
%T 466,468,469,484,486,488,494,496,498,644,646,648,649,664,666,668,669,
%U 684,686,688,694,696,698,699,844,846,848,849,864,866,868,869,884,886
%N Composite numbers in which all substrings are composite.
%C Subsequence of A062115, A202260, A029581.
%C Supersequence of A202265.
%C This is a 10-automatic sequence, see A071062. - _Charles R Greathouse IV_, Jan 01 2012
%H Rémy Sigrist, <a href="/A202262/b202262.txt">Table of n, a(n) for n = 1..10000</a>
%H Rémy Sigrist, <a href="/A202262/a202262.gp.txt">PARI program for A202262</a>
%H <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>
%t sub[n_] := Block[{d = IntegerDigits[n]}, Union@ Reap[ Do[Sow@ FromDigits@ Take[d, {i, j}], {j, Length@ d}, {i, j}]][[2, 1]]]; Select[ Range@ 900, Union[{4, 6, 8, 9}, IntegerDigits[#]] == {4, 6, 8, 9} && AllTrue[sub[#], CompositeQ] &] (* _Giovanni Resta_, Dec 20 2019 *)
%o (PARI) See Links section.
%Y Cf. A085823 (primes in which all substrings are primes), A068669 (noncomposite numbers in which all substrings are noncomposite), A062115 (nonprimes in which all substrings are nonprimes).
%Y Cf. A010051.
%K nonn,base
%O 1,1
%A _Jaroslav Krizek_, Dec 25 2011
%E Data corrected by _Reinhard Zumkeller_, May 05 2012
%E Data corrected by _Rémy Sigrist_, Dec 19 2019
%E Incorrect Haskell program deleted by _M. F. Hasler_, Dec 20 2019
|
