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A182775 Giza nonprimes. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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.

LINKS

Table of n, a(n) for n=1..31.

FORMULA

A018252 INTERSECT A134810.

EXAMPLE

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

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 *)

CROSSREFS

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

Sequence in context: A202266 A232541 A076612 * A046354 A046357 A227947

Adjacent sequences:  A182772 A182773 A182774 * A182776 A182777 A182778

KEYWORD

nonn,base,easy,fini

AUTHOR

Omar E. Pol, Dec 16 2010

STATUS

approved

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Last modified February 23 18:13 EST 2019. Contains 320437 sequences. (Running on oeis4.)