A182775 Giza nonprimes.

1, 4, 6, 8, 9, 121, 232, 343, 454, 565, 676, 898, 12321, 23432, 45654, 56765, 67876, 78987, 1234321, 2345432, 3456543, 4567654, 5678765, 6789876, 123454321, 234565432, 456787654, 567898765, 12345654321, 23456765432, 45678987654

Offset: 1

Author

Omar E. Pol, Dec 16 2010

Keywords

• nonn
• base
• easy
• fini

Comments

I propose the name Giza nonprimes.

The total number of terms is 37. The largest is 12345678987654321 which is also the largest mountain number A134941.

Examples

			a(6)=121 is in the sequence because 121 is a nonprime number A018252 and 121 is also a Giza number A134810.
The last six terms of this finite sequence are
a(32) = 1234567654321
a(33) = 2345678765432
a(34) = 3456789876543
a(35) = 123456787654321
a(36) = 234567898765432
a(37) = 12345678987654321
Illustration of a(37) as a Giza nonprime:
. . . . . . . . 9 . . . . . . . .
. . . . . . . 8 . 8 . . . . . . .
. . . . . . 7 . . . 7 . . . . . .
. . . . . 6 . . . . . 6 . . . . .
. . . . 5 . . . . . . . 5 . . . .
. . . 4 . . . . . . . . . 4 . . .
. . 3 . . . . . . . . . . . 3 . .
. 2 . . . . . . . . . . . . . 2 .
1 . . . . . . . . . . . . . . . 1
		

Crossrefs

Cf. A018252, A134810, A134811, A134941, A182776.

Programs

Mathematica

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 *)

Formula

A018252 INTERSECT A134810.