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 A202274 Positive integers m in increasing order determined by these rules: a(1) = 1, for n>=1,  if m is in the sequence then also are numbers h such that sigma(h) = 4m-1. 1
 1, 2, 4, 8, 16, 25, 32, 64, 128, 256, 512, 1024, 2048, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648, 4294967296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If 31 is only number h of form 2^k-1 for any k>=1 such that sigma(x) = h has solution for more than one value of x then a(n) is union number 25 with A000079 (powers of 2). LINKS EXAMPLE m=1, 4m-1=3, sigma(h)=3 for h=2; number 2 is in sequence. m=2, 4m-1=7, sigma(h)=7 for h=4; number 4 is in sequence. m=4, 4m-1=15, sigma(h)=15 for h=8; number 8 is in sequence. m=8, 4m-1=31, sigma(h)=31 for h=16 and 25; numbers 16 and 25 are in sequence. CROSSREFS Cf. A000203, A002191, A202273. Sequence in context: A119311 A305183 A112992 * A070789 A302588 A319385 Adjacent sequences:  A202271 A202272 A202273 * A202275 A202276 A202277 KEYWORD nonn AUTHOR Jaroslav Krizek, Dec 25 2011 STATUS approved

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Last modified October 17 08:36 EDT 2019. Contains 328107 sequences. (Running on oeis4.)