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A153874
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Numbers n = abc...k such that a^2*b^2*c^2*...k^2 - 1 = n.
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0
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..3.
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EXAMPLE
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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.
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MATHEMATICA
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Select[Range[12000], #==Times@@(IntegerDigits[#]^2)-1&] (* Harvey P. Dale, Feb 06 2022 *)
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PROG
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(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)))
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CROSSREFS
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Sequence in context: A176876 A257767 A158136 * A003902 A261074 A213337
Adjacent sequences: A153871 A153872 A153873 * A153875 A153876 A153877
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KEYWORD
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base,nonn,fini,full,bref
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AUTHOR
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Vikram Pandya, Jan 03 2009
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EXTENSIONS
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Edited by N. J. A. Sloane, Jan 03 2009
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STATUS
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approved
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