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%I #12 Nov 21 2013 12:50:06
%S 1,4,6,8,9,121,232,343,454,565,676,898,12321,23432,45654,56765,67876,
%T 78987,1234321,2345432,3456543,4567654,5678765,6789876,123454321,
%U 234565432,456787654,567898765,12345654321,23456765432,45678987654
%N Giza nonprimes.
%C I propose the name Giza nonprimes.
%C The total number of terms is 37. The largest is 12345678987654321 which is also the largest mountain number A134941.
%F A018252 INTERSECT A134810.
%e a(6)=121 is in the sequence because 121 is a nonprime number A018252 and 121 is also a Giza number A134810.
%e The last six terms of this finite sequence are
%e a(32) = 1234567654321
%e a(33) = 2345678765432
%e a(34) = 3456789876543
%e a(35) = 123456787654321
%e a(36) = 234567898765432
%e a(37) = 12345678987654321
%e Illustration of a(37) as a Giza nonprime:
%e . . . . . . . . 9 . . . . . . . .
%e . . . . . . . 8 . 8 . . . . . . .
%e . . . . . . 7 . . . 7 . . . . . .
%e . . . . . 6 . . . . . 6 . . . . .
%e . . . . 5 . . . . . . . 5 . . . .
%e . . . 4 . . . . . . . . . 4 . . .
%e . . 3 . . . . . . . . . . . 3 . .
%e . 2 . . . . . . . . . . . . . 2 .
%e 1 . . . . . . . . . . . . . . . 1
%t Select[Union[FromDigits/@Select[Flatten[Table[Table[Join[Range[i,i+n], Reverse[ Most[ Range[ i,i+n]]]],{n,0,9}],{i,9}],1],Max[#]<10&]], !PrimeQ[#]&] (* _Harvey P. Dale_, Aug 23 2011 *)
%Y Cf. A018252, A134810, A134811, A134941, A182776.
%K nonn,base,easy,fini
%O 1,2
%A _Omar E. Pol_, Dec 16 2010
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