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 A307331 The number of Ulam numbers below 10^n. 0
 6, 26, 125, 827, 7584, 74083, 740368, 7399353, 73976842, 739778038, 7397814233, 73979274540 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The terms a(1)-a(12) are from the paper by Gibbs and McCranie. The number of Ulam numbers not exceeding 10^n can be calculated from this sequence using the fact that up to 10^12 the only powers of 10 that are Ulam numbers are 10^6 and 10^11. The asymptotic density D of Ulam numbers is known to be 0 <= D <= 0.4. Gibbs and McCranie estimated it from this sequence as ~ 0.073979. LINKS Philip Gibbs, Judson McCranie, The Ulam Numbers up to One Trillion, (2017). CROSSREFS Cf. A002858. Sequence in context: A283341 A046647 A233075 * A298625 A046233 A140231 Adjacent sequences:  A307328 A307329 A307330 * A307332 A307333 A307334 KEYWORD nonn,more AUTHOR Amiram Eldar, Apr 02 2019 STATUS approved

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Last modified January 19 12:52 EST 2020. Contains 331049 sequences. (Running on oeis4.)