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A084476 Least k such that 10^(2n-1)+k is a brilliant number. 3
0, 3, 13, 43, 81, 147, 73, 3, 831, 49, 987, 691, 183, 4153, 279, 667, 709, 277, 1687, 997, 1207, 91, 1411, 393, 951, 9793, 2217, 6229, 2317, 213, 399, 19, 2317, 609, 2607, 11901, 10563, 5473, 3, 5923, 17527, 8569, 16701, 11989, 9757, 6489, 3489, 2899 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Least brilliant number greater than 10^(2n) is {10^n+A033873(n)}^2. The web site also lists the two prime factors.

LINKS

Harry Metrebian, Table of n, a(n) for n = 1..65

Dario Alejandro Alpern, Brilliant numbers

EXAMPLE

a(3)=13 because 10^5+13 = 100013 = 103*971.

MATHEMATICA

NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; LengthBase10[n_] := Floor[ Log[10, n] + 1]; f[n_] := Block[{k = 0}, If[ EvenQ[n] && n > 1, NextPrim[ 10^(n/2)]^2 - 10^(n/2), While[fi = FactorInteger[10^n + k]; Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ fi] != 2 || Length[ Union[ LengthBase10 /@ Flatten[ Table[ # [[1]], {1}] & /@ fi]]] != 1, k++ ]; k]]; Table[ f[2n + 1], {n, 1, 24}]

CROSSREFS

Cf. A078972, A084475.

Sequence in context: A267455 A138249 A181604 * A289413 A247584 A049173

Adjacent sequences:  A084473 A084474 A084475 * A084477 A084478 A084479

KEYWORD

base,hard,nonn

AUTHOR

Robert G. Wilson v, Jun 27 2003

STATUS

approved

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Last modified October 23 14:54 EDT 2019. Contains 328345 sequences. (Running on oeis4.)