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A248648 The squares related to the strictly increasing subsequence of A053667(n), n >= 1. 2
1, 4, 9, 25, 36, 49, 169, 256, 289, 576, 676, 1849, 3844, 3969, 5776, 6889, 26896, 27889, 55696, 69696, 97969, 339889, 376996, 499849, 678976, 698896, 779689, 2679769, 2768896, 2778889, 4695889, 4999696, 9696996, 26697889, 28879876, 36759969, 37994896 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The triangular numbers of this form are at A246753.
LINKS
EXAMPLE
5 * 5 = 25 is a square and the product of its digits = 2 * 5 = 10. Because a(3) = 9, and 4 * 4 = 16 has product of digits 6 < 9, a(4) = 25 because 10 > 9. The next entry a(5) comes from 6 * 6 = 36 with product of digits 18 > 10.
From Wolfdieter Lang, Oct 31 2014: (Start)
A053667 is sieved (from the left to the right):
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, ...
1, 4, 9, 6, 10, 18, 36, 24, 8, 0, 2, 16, 54, 54, ...
1, 4, 9, x, 10, 18, 36, x, x, x, x, x, 54, x, ...
and the related leftover squares are
1, 4, 9, 25 36, 49, 169, ...
(End)
-------------------------------------------------------
MATHEMATICA
A248648 = {}; k = 0; Do[s = Apply[Times, IntegerDigits[n^2]]; If[s > k, k = s; AppendTo[A248648, n^2]], {n, 1, 10^4}]; A248648
PROG
(PARI)
product=0; for(n=1, 10^5, d=digits(n^2); p=prod(i=1, #d, d[i]); while(p>product, print1(n^2, ", "); product=p)) \\ Derek Orr, Oct 11 2014
CROSSREFS
Sequence in context: A111245 A366243 A062503 * A063577 A087058 A046659
KEYWORD
nonn,base,easy
AUTHOR
K. D. Bajpai, Oct 10 2014
EXTENSIONS
Edited, Name specified, example reformulated, A053667 and 'easy' added. - Wolfdieter Lang, Oct 31 2014
STATUS
approved

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Last modified March 29 05:16 EDT 2024. Contains 371264 sequences. (Running on oeis4.)