This amusing puzzle could be nicknamed "The 25 tease". One may first see that 25 is a pair in the middle row of block 8 leaving 469 in the upper row of the blcok, but nothing to do there. So the next 25 is an oblique pair in the middle and right columns of block 1; a quick look to the right and you know there is no chance of disambiguating that, so forget it again except that now the NY Times have given you everything needed for a flurry of activity: 1 in R1C!, sounds good- 7 below that 1. Another 1 in R3C4 6 in R3C6. 9 in R1C8 - 7 in R3C8 - 3s as a pair either side of the 1 in the middle row of block 3 - 84 as a pair in the middle row of block 2 3 and 7 in the upper row of that block. And yes, the 25s refusing to cooperate. But the 25s continue to give you a lot: you can now return to block 8 downstairs : the 25 there is still unsolved, but you can now place the 649 in that order thanks to the work done upstairs. The quickest and easier way the friendly NYT algorythm gives you to break the 25 curse is when, as you did, the 9 had been placed in block 9, and you spotted the 13 pair in the upper row either side of the 5. At that juncture, there was a big telegraphic message in the form of the given 468 pointing from upwards along column 9 telling the player those digits were due to be squeezed as a triple in the 3 remaIning cells in the middle and left columns of block 9, leaving the 2 as a naked single in R9C9. Adios puzzle. Quite enjoyable, but in effect, it is just a matter of looking and taking what the block patterns give you.
