A202262 Composite numbers in which all substrings are composite.

4, 6, 8, 9, 44, 46, 48, 49, 64, 66, 68, 69, 84, 86, 88, 94, 96, 98, 99, 444, 446, 448, 464, 466, 468, 469, 484, 486, 488, 494, 496, 498, 644, 646, 648, 649, 664, 666, 668, 669, 684, 686, 688, 694, 696, 698, 699, 844, 846, 848, 849, 864, 866, 868, 869, 884, 886

Offset

1,1

Comments

Subsequence of A062115, A202260, A029581.

Supersequence of A202265.

This is a 10-automatic sequence, see A071062. - Charles R Greathouse IV, Jan 01 2012

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, PARI program for A202262

Index entries for 10-automatic sequences

Mathematica

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 *)

Prog

(PARI) See Links section.

Crossrefs

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).

Cf. A010051.

Sequence in context: A113624 A113591 A029581 * A202266 A232541 A076612

Adjacent sequences: A202259 A202260 A202261 * A202263 A202264 A202265

Keyword

nonn,base

Author

Jaroslav Krizek, Dec 25 2011

Extensions

Data corrected by Reinhard Zumkeller, May 05 2012

Data corrected by Rémy Sigrist, Dec 19 2019

Incorrect Haskell program deleted by M. F. Hasler, Dec 20 2019

Status

approved