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47, 51, 59, 67, 75, 79, 175, 179, 187, 195, 203, 207, 291, 299, 339, 347, 419, 427, 467, 475, 531, 539, 611, 619, 659, 667, 739, 747, 767, 771, 779, 815, 831, 847, 883, 891, 899, 907, 943, 959, 975, 1011, 1019, 1027, 1035, 1087, 1139, 1147, 1155, 1163, 1215
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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These are the indices to A193231 where the count of 1-bits in its terms changes by more than one.
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LINKS
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EXAMPLE
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47 is in the sequence, as A193231(47) = 59, A193231(48) = 34, and A007088(59)='111011', A007088(34)='100010', thus there are five 1-bits in the former, while there are only two in the latter, and abs(5-2) = 3 > 1.
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PROG
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(Python)
def a065621(n): return n^(2*(n - (n&-n)))
def a048724(n): return n^(2*n)
def a193231(n):
if n<2: return n
if n%2==0: return a048724(a193231(n//2))
else: return a065621(1 + a193231((n - 1)//2))
def a234022(n): return bin(a193231(n))[2:].count("1")
def ok(n): return abs(a234022(n) - a234022(n + 1))>1
print([n for n in range(1, 1501) if ok(n)]) # Indranil Ghosh, Jun 05 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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