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 A175888 Numbers n with property that sigma(n) < min(sigma(n-2),sigma(n-1),sigma(n+1),sigma(n+2)). 3
 11, 17, 23, 29, 37, 41, 47, 53, 59, 67, 71, 79, 83, 89, 97, 101, 107, 113, 121, 127, 131, 137, 143, 149, 157, 163, 167, 173, 179, 187, 191, 197, 203, 211, 217, 223, 227, 233, 239, 247, 251, 257, 263, 269, 277, 281, 289, 293, 299, 307, 311, 317, 323, 331, 337 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Strict local minimums of sigma(n) of the 2nd order: sigma(n) is less than any of 4 closest neighbors. b(n) = the first term ending with n=1..9: 11,22683662,23,17254,635,69686,17,6143138,29 c(n) = position of b(n) in the sequence: 1,3781722,3,2872,105,11608,2,1024132,4. The term in the sequence ending with zero should be very large (>~10^80 according to Charles R Greathouse IV). LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA sminQ[{a_, b_, c_, d_, e_}]:=c

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Last modified April 3 00:35 EDT 2020. Contains 333195 sequences. (Running on oeis4.)