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 A324317 Number of primary Carmichael numbers (A324316) less than 10^n. 10
 0, 0, 0, 2, 4, 9, 19, 51, 107, 219, 417, 757, 1470, 2666, 5040, 9280, 17210, 32039, 59762 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS The number of Carmichael numbers (A002997) less than 10^n is 0, 0, 1, 7, 16, 43, 105, 255, 646, 1547, 3605, 8241, 19279, 44706, 105212, 246683, 585355, 1401644, ... (see A055553). The terms up to a(10) are given in Table 1 of Kellner and Sondow 2019. The terms up to a(18) and related results are given in Table 1.5 of Kellner 2019. All computations depend on Pinch's database. LINKS Table of n, a(n) for n=1..19. Bernd C. Kellner and Jonathan Sondow, Power-Sum Denominators, Amer. Math. Monthly, 124 (2017), 695-709; arXiv:1705.03857 [math.NT], 2017. Bernd C. Kellner and Jonathan Sondow, On Carmichael and polygonal numbers, Bernoulli polynomials, and sums of base-p digits, #A52 Integers 21 (2021), 21 pp.; arXiv:1902.10672 [math.NT], 2019. Bernd C. Kellner, On primary Carmichael numbers, #A38 Integers 22 (2022), 39 pp.; arXiv:1902.11283 [math.NT], 2019. R. G. E. Pinch, The Carmichael numbers up to 10^18, 2008. EXAMPLE There are two primary Carmichael numbers less than 10^4, namely, 1729 and 2821, so a(4) = 2. CROSSREFS Cf. A002997, A055553, A324315, A324316, A324318, A324319, A324320, A324369, A324370, A324371, A324404, A324405. Sequence in context: A153447 A076893 A176501 * A096354 A076838 A034749 Adjacent sequences: A324314 A324315 A324316 * A324318 A324319 A324320 KEYWORD nonn,base,more,hard AUTHOR Bernd C. Kellner and Jonathan Sondow, Feb 22 2019 EXTENSIONS a(11)-a(18) from Amiram Eldar, Mar 01 2019 a(19) from Amiram Eldar, Dec 05 2020 STATUS approved

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Last modified December 10 18:13 EST 2023. Contains 367717 sequences. (Running on oeis4.)