A334021
Numbers k such that s(k) = s(k+1) = s(k+2), where s(k) is the sum of unitary divisors of k that are smaller than sqrt(k) (A334019).
Original entry on oeis.org
2, 3, 7, 1420, 2505, 11860, 64060, 64485, 113413, 158020, 205365, 332658, 465272, 522764, 611085, 614538, 635053, 664033, 748484, 771138, 839213, 881565, 1011793, 1090788, 1190685, 1248645, 1306605, 1488088, 1607367, 1613190, 1836018, 1884914, 1911940, 2286913
Offset: 1
2 is a term since A334019(2) = A334019(3) = A334019(4) = 1.
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s[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; seq={}; s1 = s[1]; s2 = s[2]; Do[s3 = s[n]; If[s1 == s2 && s2 == s3, AppendTo[seq, n - 2]]; s1 = s2; s2 = s3, {n, 3, 10^5}]; seq
A334022
Numbers k such that s(k) = s(k+1) = s(k+2) = s(k+3), where s(k) is the sum of unitary divisors of k that are smaller than sqrt(k) (A334019).
Original entry on oeis.org
2, 46351754, 102841142, 158071592, 667930085, 851043553, 1097409992, 1580045430, 1595193655, 1698842487, 1919035496, 1951958341, 2279249234, 2507918727, 2520080695, 2741951910, 3335769314, 3654512455, 3713106152, 4209598844, 4351540982, 4369408604, 4480814965
Offset: 1
2 is a term since A334019(2) = A334019(3) = A334019(4) = 1.
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s[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; seq={}; s1 = s[1]; s2 = s[2]; s3 = s[3]; Do[s4 = s[n]; If[s1 == s2 && s2 == s3 && s3 == s4, AppendTo[seq, n - 3]]; s1 = s2; s2 = s3; s3 = s4, {n, 4, 10^9}]; seq
A334024
Numbers k such that s(k) = s(k+1), where s(k) is the sum of unitary divisors of k that are larger than sqrt(k) (A334023).
Original entry on oeis.org
24752, 101972, 14257705
Offset: 1
24752 is a term since A334023(24752) = A334023(24753) = 33896.
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s[n_] := DivisorSum[n, # &, #^2 > n && CoprimeQ[#, n/#] &]; Select[Range[1.5*10^7], s[#] == s[# + 1] &]
Showing 1-3 of 3 results.
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