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 A063964 Numbers k such that k and k+1 have the same sum of squarefree divisors, or sqf(k) = sqf(k+1), where sqf(k) = A048250(k). 1
 11, 14, 224, 957, 1334, 1634, 2685, 9347, 13915, 16260, 20145, 20335, 33998, 37236, 42251, 42818, 51624, 55308, 56419, 56975, 71874, 74918, 77748, 79824, 79826, 79833, 84134, 93632, 106600, 111506, 120680, 122073, 138237, 142116, 147454 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..1000 (terms 1..170 from Harry J. Smith) MATHEMATICA sqs[n_] := Times@@(1 + FactorInteger[n][[;; , 1]]); seq={}; s1 = 1; Do[s2 = sqs[n]; If[s2 == s1, AppendTo[seq, n-1]]; s1 = s2, {n, 2, 10^5}]; seq (* Amiram Eldar, Aug 18 2019 *) PROG (PARI) sqf(n) = sumdiv(n, d, if(issquarefree(d), d, 0)); for(n=1, 10^7, if(sqf(n)==sqf(n+1), print(n))) (PARI) { n=0; s=0; for (m=1, 10^9, t=sumdiv(m + 1, d, if(issquarefree(d), d, 0)); if(s==t, write("b063964.txt", n++, " ", m); if (n==170, break)); s=t ) } \\ Harry J. Smith, Sep 04 2009 CROSSREFS Cf. A048250. Sequence in context: A195818 A101840 A061087 * A262721 A174952 A209898 Adjacent sequences:  A063961 A063962 A063963 * A063965 A063966 A063967 KEYWORD easy,nonn AUTHOR Jason Earls, Sep 04 2001 STATUS approved

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Last modified October 22 22:34 EDT 2019. Contains 328335 sequences. (Running on oeis4.)