A153874 Numbers n = abc...k such that a^2*b^2*c^2*...k^2 - 1 = n.

143, 323, 11663

Offset

1,1

Links

Table of n, a(n) for n=1..3.

Example

1) 143 = 1^2 * 4^2 * 3^2 - 1 = 1 * 16* 9 - 1. 2) 323 = 3^2 * 2^2 * 3^2 - 1 = 9 * 4 * 9 - 1. 3) 1663 = 1^2 * 1^2* 6^2 * 6^2 * 3^2 - 1 = 1 * 1 * 36 * 36 * 9 - 1.

Mathematica

Select[Range[12000], #==Times@@(IntegerDigits[#]^2)-1&] (* Harvey P. Dale, Feb 06 2022 *)

Prog

(PARI) n=1; while(n!=10^16, n+=1; j=n^2-1; k=1; while(j!=0, k=k*(j%10)^2; j=floor(j/10)); if(k-1==n^2-1, print(n^2-1)))

Crossrefs

Sequence in context: A176876 A257767 A158136 * A003902 A261074 A213337

Adjacent sequences: A153871 A153872 A153873 * A153875 A153876 A153877

Keyword

base,nonn,fini,full,bref

Author

Vikram Pandya, Jan 03 2009

Extensions

Edited by N. J. A. Sloane, Jan 03 2009

Status

approved